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Full text of "Transactions of the Royal Society of Edinburgh"

/ 



S.ir.CM- 






TRANSACTIONS 



OF THE 



EOYAL SOCIETY OF EDINBURGH. 

VOL. XXXVII. PART L— (Nos. 1 to 14)— FOR THE SESSION 1891-92. 



CONTENTS. 




I. The Chemistry of Strophanthidin, a Decomposition Product of Strophanthin. 

Feaseb, M.D., F.R.S., and Leonard Dobbin, Ph.D., .... 

II. Circular Magnetisation* accompanying Axial and Sectional Currents along Iron Tubes. 

Professor Cargill G. Knott, D.Sc., E.R.S.E. (With Plate), ... 7 

III. On the Number of Dust Particles in the Atmosphere of certain Places in Great Britain and on 

the Continent, with Remarks on the Relation between the Amount of Dust and Meteoro- 
logical Phenomena. By John Aitken, F.li.S. (With Plate), . . . .17 

IV. On the New Star in the Constellation Auriga. By Professor Ralph Copeland, Astronomer- 

Royal for Scotland. Together with Observations of the Same. By Dr L. Becker. (With 

a Plate), . . . . . . . . . . 51 

V. The Lateral Sense Organs of Elasmobranchs. I. The Sensory Canals of Laemargus. By J. C. 
Ewart, M.D., Regius Professor of Natural History, University of Edinburgh. (Plates 
I. and II.), .......... 59 

VI. On the Lateral Sense Organs of Elasmobranchs. II. The Sensory Canals of the Common Skate 
(Raia batis). By J. C. Ewart, M.D., Regius Professor of Natural History, and J. C. 
Mitchell, B.Sc., University of Edinburgh. (Plate III.), . . . .87 

VII. On the Latest Phase* of Literary Style in Greece. By Emeritus Professor Blackie, . .107 

VIII. The Lower Carboniferous Volcanic Rocks of East Lothian (Carlton Hills). By Frederick II. 
Hatch, Ph.D., F.G.S., of the Geological Survey. Communicated by Sir Archibald 
Geikie, F.R.S. (With Two Plates), . . . . . .115 

IX. On the Glacial Succession in Europe. By Professor James Geikie, D.C.L., LL.D., F.R.S. , &c. 

(With a Map), 127 

X. On some Eurypterid Remains from the Upper Silurian Rocks of the Pentland Hills. By 

Malcolm Laurie, B.Sc, F.L.S. (With Three Plates), . . . . .151 

XL On Borolanite — an Igneous Rock intrusive in the Cambrian Limestone of Assynt, Sutherland- 
shire, and the Torridon Sandstone of Ross-shire. By J. Horne, F-RS.E., and J. J. H. 
Teall, F.R.S., of the Geological Survey. (Communicated by permission of the Director- 
General of the Geological Survey. (With a Plate), ..... 163 

XII. On the Action of the Valves of the Mammalian Heart. By D. Noel Paton, M.D., F.R.C.P.E., 
Superintendent of the Research Laboratory of the Royal College of Physicians. (With 
Two Plates), .......... 179 

XIII. A Contribidion to the Anatomy of Sutroa. By Frank E. Beddard, M.A., Prosector to the 

Zoological Society of London. (With a Plate), . . . . . .195 

XIV. A Comparison of the Minute Structure of Plant Hybrids with that of their' Parents, and its 

Rearing on, Biological Problems. By J. Muirhead Macfarlane, D.Sc, F.R.S.E. 
(Plates I.-VIIL), ' 203 



EDINBURGH: 

PUBLISHED BY ROBERT GRANT & SON, 107 PRINCES STREET, 
AND WILLIAMS & NORGATE, 14 HENRIETTA STREET, COVENT GARDEN, LONDON. 



MDCCCXCIII. 
(Issued February 17, 1893.) 



TEANSACTIONS 



OF THE 



ROYAL SOCIETY OF EDINBURGH 



Q h. C.3Z- 



TRANSACTIONS 



OF THE 



ROYAL SOCIETY 



OF 



EDINBURGH. 



VOL. XXXVII. 




EDINBURGH: 

PUBLISHED BY ROBERT GRANT & SON, 107 PRINCES STREET. 
AND WILLIAMS & NORGATE, 14 HENRIETTA STREET, COVENT GARDEN, LONDON. 



MDCCCXCV. 



No. 



I. 


Published 


March 23, 1892. 


No. 


XVIII. 


Published 


II. 


>> 


June 13, 1892. 


JJ 


XIX. 


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III. 


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XX. 


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IV. 


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July 7, 1892. 


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XXI. 


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August 5, 1892. 


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XXII. 


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VI. 


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XXIII. 


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VII. 


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August 19, 1892. 


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XXIV. 


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VIII. 


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August 20, 1892. 


JJ 


XXV. 


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IX. 


>> 


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XXVI. 


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X. 


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September 26, 1892. 


)> 


XXVII. 


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XI. 


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November 2, 1892. 


V 


XXVIII. 


>> 


XII. 


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November 5, 1892. 


>> 


XXIX. 


)) 


XIII. 


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November 3, 1892. 


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XXX. 


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XIV. 


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November 10, 1892. 


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XXXI. 


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XV. 


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December 5, 1892. 


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XXXII. 


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XVI. 


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January 17, 1893. 


)J 


XXXIII. 


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XVII. 


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March 29, 1893. 


>> 


XXXIV 


>> 



February 24, 1893. 
April 12, 1893. 
July 28, 1893. 
August 26, 1893. 
September 16, 1893. 
September 15, 1893. 
October 3, 1893. 
November 13, 1893. 
March 28, 1894. 
May 1, 1894. 
June 20, 1894. 
July 12, 1894. 
October 15, IS!) 1. 



February 13, 1895. 
February 8, 1895. 



CONTENTS. 



PART I. (1891-92.) 

NUMBEU PAGE 

I. The Chemistry of Strophanthidin, a Decomposition Product of Strophan- 
thin. By Thomas R. Fraser, M.D., F.R.S., and Leonard Dobbin, 
Ph.D., 1 

II. Circular Magnetisations accompanying Axial and Sectional Currents 
along Iron Tubes. By Professor Cargill G. Knott, D.Sc, F.R.S.E. 
(With a Plate), ....... 7 

III. On the Number of Dust Particles in the Atmosphere of certain Places in 

Great Britain and on the Continent, with Remarks on the Relation 
between the Amount of Dust and Meteorological Phenomena. By John 
Aitken, F.R.S. (With a Plate), . . . . .17 

IV. On the New Star in the Constellation Auriga. By Professor Ralph 

Copeland, Astronomer-Royal for Scotland. Together with Observa- 
tions of the Same. By Dr L. Becker. (With a Plate), . . 51 

V. The Lateral Sense Organs of Elasmobranchs. I. The Sensory Canals of 
Lcemai'gus. By J. C. Ewart, M.D., Regius Professor of Natural 
History, University of Edinburgh. (Plates I. and II.), . . 59 

VI. On the Lateral Sense Organs of Elasmobranchs. II. The Sensory Canals 
of the Common Skate (Raia batis). By J. C. Ewart, M.D., Regius 
Professor of Natural History, and J. C. Mitchell, B.Sc, University 
of Edinburgh. (Plate III), ...... 87 



vi CONTENTS. 



PAGE 



VII. On the Latest Phases of Literary Style in Greece. By Emeritus Pro- 
fessor Blackie, . . . . . . .107 

VIII. The Lower Carboniferous Volcanie Bocks of East Lothian (Garlton Hills). 
By Frederick H. Hatch, Ph.D., F.G.S., of the Geological Survey. 
Communicated by Sir Archibald Geikie, F.R.S. (With Two Plates), 115 

IX. On the Glacial Succession in Europe. By Professor James Geikie, 

D.C.L., LL.D., F.K.S., &c. (With a Map), . . . 127 

X. On some Euryptericl Remains from the Upper Silurian Rocks of the 
Pentland Hills. By Malcolm Laurie, B.Sc, F.L.S. (With Three 
Plates), ........ 151 

XI. On Borolanite — an Igneous Rock intrusive in the Cambrian Limestone of 
Assynt, Sutherlandshire, and the To?'ridon Sandstone of Ross-shire. 
By J. Horne, F.R.S.E., and J. J. H. Teall, F.E.S., of the Geo- 
logical Survey. (Communicated by permission of the Director- 
General of the Geological Survey.) (With a Plate), . .163 

XII. On the Action of the Valves of the Mammalian Heart. By D. Noel 
Paton, M.D., F.R.C.P.E., Superintendent of the Research Labo- 
ratory of the Royal College of Physicians. (With Two Plates), . 179 

XIII. A Contribution to the Anatomy of Sutroa. By Frank E. Beddard, 

M.A., Prosector to the Zoological Society of London. (With a 
Plate), ......... 195 

XIV. A Comparison of the Minute Structure of Plant Hybrids with that of 

their Parents, and its Bearing on Biological Problems. By J. Muir- 
head Macfarlane, D.Sc, F.R.S. E. (Plates I. -VIII.), . . 203 



PART II. (1892-93.) 

XV. The Skull and Visceral Skeleton of the Greenland Shark, Laemargus 
microcephalus. By Philip J. White, M.B., Demonstrator of 
Zoology, University of Edinburgh. Communicated by Professor 
Ewart. (With Two Plates), . . . . .28 



CONTENTS. VH 

NUMBER PAGK 

XVI. On the Fossil Plants of the Kilmarnock, Galston, and Kilwinning Coal 
Fields, Ayrshire. By Kobert Kidston, F.E.S.E., F.G.S. (Plates 
I.-IV.), . . .307 

XVII. Electrolytic Synthesis of Dibasic Acids. By Professor A. Crum Brown 
and Dr James Walker. II. On the Electrolysis of the Ethyl- 
Potassium Salts of Saturated Dibasic Acids with Side Chains, and 
on Secondary Reactions accompanying the Electrolytic Synthesis of 
Dibasic Acids, ....... 361 

XVIII. On Impact, II. By Professor Tait, . . . . .381 

XIX. A New Algebra, by means of which Permutations can be transformed 
in a variety of ways, and their properties investigated. By T. B. 
Sprague, M.A., F.RS.E., ...... 399 

XX. On the Particles in Fogs and Clouds. By John Aitken, Esq., F.R.S., 

F.RS.E., . . . . . . . .413 

XXI. On the Path of a Rotating Spherical Projectile. By Professor Tait. 

(With a Plate), 427 

XXII. On the Present State of Knowledge and Opinion in regard to Colour- 
Blindness. By William Pole, F.R.S., F.RS.E., Mus. Doc. Oxon., 
Honorary Secretary of the Institution of Civil Engineers. (With 
a Plate), ........ 441 

XXIII. On the Chemical Changes which take place in the Composition of 

the Sea-Water associated with Blue Muds on the Floor of the 
Ocean. By John Murray, LL.D., Ph.D., and Robert Irvine, 
F.C.S., 481 

XXIV. The Anatomy and Relations of the Eurypteridos. By Malcolm 

Laurie, B.Sc, B.A., F.L.S. Communicated by R. H. Traquair, 
M.D., F.R.S., F.RS.E. (With Two Plates), . . .509 



vin 



CONTENTS. 



PAKT III. (1893-94.) 

NTM1SEK 

XXV. On Lepidophloios, and on the British Species of the Genus. 
Kobert Kidston, F.E.S.R, F.G.S. (With Two Plates), 



By 



PACK 



529 



XXVI. On the Fossil Flora of the South Wales Coal Field, and the Relation- 
ship of its Strata to the Somerset and Bristol Coal Field. By 
Robert Kidston, F.R.S.E., F.G.S. (With a Plate), 



565 



XXVII. On Bistratification in the Growth of Languages, with Special 
Reference to Greek. By Emeritus Professor Blackie, . 



615 



XXVIII. On the Number of Dust Particles in the Atmosphere of Certain Places 
in Great Britain and on the Continent, ivith Remarks on the 
Relation 'between the Amount of Dust and Meteorological Pheno- 
mena. Part III. By John Aitken, F.R.S. (With Three 
Plates), . . . . ... . .621 

XXIX. On the Variations of 'the Amount of Carbonic Acid in the Ground- 
Air {Grund-Luft of Pettenkofer). By C. Hunter Stewart, 
B.Sc., M.B. (From the Public Health Laboratory of the 
University of Edinburgh.) (With Three Plates), . . 695 



PART IV. (1894-95.) 

XXX. Note on some Fossils from Seymour Island, in the Antarctic Regions, 
obtained by Dr Donald. By G. Sharman and E. T. Newton. 
(With a Plate), . . . . . 



707 



XXXI. On the Partition of a Parallelepiped into Tetrahedra, the Corners of 
which Coincide with Cornel's of the Parallelepiped. By Professor 
Crum Brown. (With Two Plates), . . . .711 

XXXII. On the Manganese Oxides and Manganese Nodules in Marine 
Deposits. By John Murray, LL.D., Ph.D., of the Challenger 
Expedition, and Robert Irvine, F.C.S., . . . . 721 



CONTENTS. 



IX 



XXXIII. I. — On the Estimation of Carbon in Organic Substances by the Kjel- 
dahl Method. II. — Its Application to the Analysis of Potable 
Waters. By Charles Hunter Stewart, D.Sc, M.B. (From 
the Public Health Laboratory of the University of Edinburgh.) 
(With Two Plates), . . . .743 

XXX I Vl The Chemical and Bacteriological Examination of Soil, ivith special 
reference to the Soil of Graveyards. By James Buchanan 
Young, M.B., D.Sc. (From the Public Health Laboratory, 
University of Edinburgh), . . . . . 759 



Appendix - 



The Council of the Society, ...... 778 

Alphabetical List of the Ordinary Fellows, .... 779 

List of Honorary Fellows, ...... 794 

List of Ordinary jffellows Elected during Session 1891-92, . . 796 

List of Honorary Fellows Elected during Session 1891-92, . . 797 

Fellows Deceased or Resigned during Session 1891-92, . . . 798 

List of Ordinary Felloivs Elected during Session 1892-93, . . 799 

Fellows Deceased or Resigned during Session 1892-93, . . 800 

List of Ordinary Felloivs Elected during Session 1893-94, . . 801 

Fellows Deceased or Resigned during Session 1893-94, . . . 802 

Laws of the Society, ....... 803 

The Keith, Makdougall-Brisbane, Neill, and Gunning Victoria Jubilee 

Prizes, ........ 810 

Awards of the Keith, Makdougall-Brisbane, and Neill Prizes, from 1827 
to 1893, and of the Gunning Victoria Jubilee Prize from 1884 to 

1893, ........ 813 

b 



CONTENTS. 



Appendix — continued. 



PAGE 



Proceedings of the Statutory General Meetings, 817 

List of Public Institutions and Individuals entitled to receive Copies of the 

Transactions and Proceedings of the Royal Society, . . 825 

Index, .....••■• 833 



TRANSACTIONS. 



I. — The Cliemistry of Strophanthidin, a Decomposition Product of Strophanthin. By 
Thomas R. Fraser, M.D., F.R.S., and Leonard Dobbin, Ph.D. 

(Read 7th December 1891. ) 

In a paper on the Chemistry and Pharmacology of Strophanthus hispidus, it was 
pointed out by one of us that when strophanthin, the glucosidal active principle present 
in the seeds and several other parts of this plant, is subjected to the action of dilute 
acids, it yields, among other products, a crystalline body — strophanthidin. A brief 
description was also given of processes by which this body may be prepared, and of 
several of its characters and chemical properties.* 

The chemistry of strophanthidin will be more fully described in the present paper. 

Preparation. — Strophanthidin may conveniently be prepared by allowing a 5°/ o 
solution of strophanthin, or of pure extract of Strophanthus, in 1*5 or 2°/ o sulphuric acid 
to stand at the ordinary temperature for a few days. When this is done, the originally 
nearly clear solution soon becomes hazy, the haziness gradually increases during the 
following day or two, and then the solution again becomes clear, much glucose is found 
to be present in it, and a deposit forms, which consists, for the most part, of crystals. The 
crystals are usually sufficiently large to be apparent to the naked eye,t but sometimes 
they are so minute that their crystalline form is recognisable only when they are magnified. 
They are slightly coloured when prepared from the extract, but are almost colourless when 
prepared from strophanthin. 

Crystalline strophanthidin may be produced in the cold not only by the action of dilute 
sulphuric acid, but also of dilute hydrochloric, nitric, phosphoric, acetic, oxalic, and 
hydrocyanic acid. It is, however, more rapidly produced by these acids at a temperature 
of from 50° to 78° C, when it often appears in the form of long friable needles, from six 
to ten millimetres in length ; but at higher temperatures, an amorphous coloured sub- 
stance, and not an almost colourless crystalline body, is obtained. 

By the above process, so much as 37 / o of crystalline strophanthidin has been obtained 

* Trans. Roy. Soc. Edin., vol. xxxv. part iv. pp. 1004-1017. t Ibid., pi. vii. fig. 10. 

VOL, XXXVII. PART I. (NO. 1). A 



2 PROFESSOR FRASER AND DR DOBBIN ON 

from strophanthin, and 30°/ o from the extract, although more frequently the extract 
yielded from 20 to 25°/ o . 

In order to effect the complete decoloration of the crystals, from whatever source they 
have been obtained, they may be washed with distilled water and digested for a few 
hours with a little pure charcoal in a hot rectified spirit solution. The filtered hot solu- 
tion deposits, on cooling, colourless crystals of considerable size, which continue to form 
on the spontaneous evaporation of the solution. The crystals consist of four-sided, 
apparently monoclinic, prisms, terminated either by the end faces alone, or also by 
pyramidal faces. To ensure the absolute purity of the product, it may several times be 
recrystallised from alcohol, or precipitated by petroleum ether or by water from a con- 
centrated solution in alcohol, or in several of the other solvents afterwards to be mentioned. 

General Characters. — The crystals are easily broken down in a mortar, but the 
particles are somewhat adhesive, and may even form a friable paste during triturition. 
A solution in water is neutral in reaction, and a moderately persistent froth is produced 
when it is shaken. A saturated watery solution is strongly, though not intensely, bitter ; 
and slight bitterness can be perceived also in a solution of one part in sixty thousand. 

Solubilities. — Unlike strophanthin, strophanthidin is insoluble in glycerine, very 
slightly soluble in cold water, only moderately soluble in rectified spirit, and more soluble 
in absolute than in dilute alcohol. Absolute alcohol and acetone, however, dissolve a 
larger quantity of it than of strophanthin. It resembles strophanthin in being insoluble 
in olive oil. 

The results of determinations of its solubility in various, liquids, at the ordinary 
temperature, are as follows : — 



Absolute ethyl alcohol (sp. gr. 796) 


1 in 


30, or 3 "3 per c 


Acetone ..... 


)5 


35, or 2-85 


Rectified spirit (sp. gr. *838) . 


59 


47, or 2-1 


Amyl alcohol (sp. gr. *820) 


5) 


165, or 0-606 


Chloroform (sp. gr. 1*497) 


)! 


690, or 0-1449 


Distilled water .... 


)5 


2150, or 0-0465 


Ethyl ether (sp. gr. 723) 


5) 


2196, or 0-0455 


Ethyl ether (sp. gr. 730) 


)J 


2222, or 0-045 


Petroleum ether (boiling below 50° C.) 


Absolutely insoluble. 



Its solubility in several of these liquids, as for example in rectified spirit, is much 
increased by elevating the temperature. After hot saturated solutions in alcohol have 
become cool, and have ceased to deposit strophanthidin, they hold in solution a larger 
quantity than alcohol is capable of dissolving without the aid of heat. 

Strophanthidin is precipitated by petroleum ether from solution in absolute alcohol, 
acetone, rectified spirit, amyl alcohol, ethyl ether, and chloroform ; and by water from 
solution in absolute alcohol and rectified spirit. Precipitation is, however, only slowly 
produced in rectified spirit and ethyl ether solutions. The precipitates, either imme- 



THE CHEMISTRY OF STROPHANTHIDIN. 3 

diately or after the lapse of several hours, assume the form of broad or needle-shaped 
rhombic crystals, which are bright and translucent. 

Ethyl ether, which so readily precipitates strophanthin from solution in ethyl and 
amyl alcohol and in acetone, fails to precipitate strophanthidin when dissolved in these 
liquids ; nor is it precipitated by ethyl alcohol, acetone, amyl alcohol, or chloroform, 
from solution in any of the liquids in which its solubility was determined. Weak alcoholic 
solutions are rendered hazy by the addition of water, even when the quantity of added 
water is itself more than sufficient to dissolve the strophanthidin present ; and a similar 
change is produced in watery solutions by the addition of a little rectified spirit. 

Melting point. — Strophanthidin melts at between 170° and 171° C, with incipient 
decomposition and the disengagement of bubbles of gas. When heated on platinum foil 
over a Bunsen's burner, it suddenly liquefies, bubbles of gas are profusely disengaged, 
combustion takes place with a bright flame, and very quickly the whole substance entirely 
disappears. No decided odour is evolved during the heating and burning. 

Specific Rotation. — It possesses positive rotation in alcoholic solution. One gramme 
dissolved in 50 c.c. of rectified spirit (sp. gr. 0*838) was found to have a specific gravity 
of 0'85, and, with a 5 decimetres column, it produced a rotation of + 4° 7', which cor- 
responds with a specific rotation of + 41° 12'. 

It was found that the specific rotation of strophanthin, in the same conditions, is 
+ 14°. 

Elementary Analysis. — When crystallised from rectified spirit, strophanthidin does 
not lose weight at 100° C. It does not contain nitrogen. When heated for two hours 
at 100° C. in 2 per cent, sulphuric acid, it is converted into a brown resin-like substance, 
but no glucose appears in the solution. A carefully purified specimen, recrystallised from 
rectified spirit, when subjected to ultimate analysis, yielded the following results, in two 
combustions : — 

1. 0*1134 gramme yielded C0 2 , 0*2746 gramme, = 66*04 per cent. C. 

H 2 0, 0*0857 „ = 8*39 „ H. 

2. 0*1150 gramme yielded C0 2 , 0*2793 „ =66*23 „ C. 

H 2 0, 0*0866 „ = 8*36 „ H. 

These percentages correspond with the formula C 14 H 22 4 . 

Found (average of Calculated for 

two analyses). C^H^O^ 

Carbon, . . . 66*13 . . 66*14 per cent, 

Hydrogen, . . 8*37 . . 8*66 

Oxygen (by subtraction), 25*50 . . 25*2 ,, 

In the absence of knowledge regarding the constitution of strophanthidin, the formula 
C 14 H 22 4 may, therefore, provisionally be adopted. 



PROFESSOR FRASER AND DR DOBBIN ON 



Reactions of Dry Strophanthidin. 

1. When strong sulphuric acid was placed in contact with a little finely powdered 
strophanthidin, an immediate orange red colour was produced, and slowly a bluish-green 
colour appeared at the margins. In 40 minutes the green colour had extended itself, 
and soon afterwards it had entirely displaced the red. The green, in its turn, slowly faded, 
and the whole then assumed a faint brownish-yellow tint, which persisted for several 
hours. After the addition of strong sulphuric acid had developed an orange-red colour, 
the subsequent addition of nitric acid immediately changed the colour to dusky yellow, 
which slowly faded to pale brownish-yellow. 

When strophanthidin, moistened with strong sulphuric acid, was slowly heated 
between 42° and 45° C, the orange-red first produced became a yellowish-red with a 
slight green tint at the margins, then altogether greenish-yellow, and finally brown. 

2. Contact in the cold with dilute sulphuric acid (10 per cent.) failed to develop any 
colour within half an hour. On now heating gradually to 48° C, yellowish-green 
appeared at the margins and yellow at the centre ; the green soon became very dark 
until it was almost black, and the yellow at the centre changed to brown ; and in about 
an hour and a half the whole assumed a brownish-black colour. 

3. Strong nitric acid produced in the cold merely a very faint brown tint, which 
appeared only after prolonged contact, but remained unchanged for several hours. On 
the addition of strong sulphuric acid, the very faint brown tint immediately became 
pinkish-yellow, which very soon changed to greenish-yellow. 

When strophanthidin was mixed with strong nitric acid, and placed in an air chamber 
with a temperature of 43° C, which was gradually raised to 52°, in one minute a faint 
pink tint appeared, which very soon changed to brownish-yellow, and in a few minutes to 
pale yellow, which slowly deepened in hue until a deep yellow, almost gamboge, was 
developed. The last colour remained for more than an hour and a half. 

4. Dilute nitric acid (10 per cent.) produced no change in the cold. When, however, 
the temperature was slowly raised to 47° and 48° C, a light orange colour was speedily 
produced, which persisted for several hours. 

5. Contact in the cold with strong hydrochloric acid merely caused the particles of 
strophanthidin to become slightly brown, even when the contact was continued for 
several hours. 

On slowly heating to from 43° to 48° C. with strong hydrochloric acid, yellow appeared 
at the edges and gradually spread over the whole surface of the mixture, and this yellow 
colour remained for several hours, during which the heating was continued. 

6. Dilute hydrochloric acid (10 per cent.) produced no change in the cold. 

On heating between 47° and 48° C, an orange colour was produced, which persisted 
for several hours. 

7. Strong sulphuric acid and bichromate of potassium produced a crimson colour, which 



THE CHEMISTRY OF STROPHANTHIDIN. 5 

passed slowly into brown with patches of green, and then the whole gradually became 
very pale brown. 

8. Strong sulphuric acid and chlorate of potassium produced a crimson colour, which soon 
became pale reddish -yellow. 

9. Phosphomolybdic acid very slowly developed a pale greenish-blue colour. When an 
alkali was added along with or after the phosphomolybdic acid, a blue colour was imme- 
diately developed. 

10. After contact with strong sulphuric acid had developed the usual orange-red colour 
in powdered strophanthidin, exposure to the vapour of bromine rapidly deepened the 
colour to a dark salmon-red, in which the undissolved ' particles of strophanthidin 
appeared black ; and, soon afterwards, the salmon-red became dusky red, and the dusky 
red, after several hours, changed to green. 

11. Solution of potash, soda, ammonia, lime, and baryta, and of carbonate of potash and 
carbonate of soda failed to produce any colour change ; and negative results were also 
obtained on the addition of iodic acid and starch, of hydrobromic acid and starch, and of nitric 
acid followed by stannous chloride. 

Reactions of Solution of Strophanthidin in Water (saturated, 1 : 2000). 

1. Solution of iodide of potassium and of potassio-mercuric iodide produced a light brown 
colour, and when this had been developed, the addition of starch solution produced the 
usual blue reaction indicative of free iodine. 

2. When to a drop of the strophanthidin solution, placed on a white porcelain slab, a 
drop of very dilute solution of ferric chloride was added, and then a drop of strong sulphuric 
acid, a yellow colour was immediately produced, and, on stirring, a faint pink tinge 
appeared, and in a few seconds the mixture became almost colourless. 

Negative results were obtained on the addition of solutions of chloride of gold, nitrate 
of silver, platinic chloride, cobaltous chloride, acetate and subacetate of lead, mercuric chloride, 
cupric sulphate, tannic acid, picric acid, ferric chloride, metatungstate of sodium, hydrobromic acid, 
bromide of potassium, tribromide of potassium and Nessler's reagent. 



VOL. XXXVII. PART I. (NO. 1). B 



( 7 ) 



II. — Circular Magnetisations accompanying Axial and Sectional Currents along Iron 
Tubes. By Professor Cargill G. Knott, D.Sc, F.K.S.E. (With Plate.) 

(Read 18th January 1892.) 

The experiments now to be described have for their object the investigation of the 
magnetic induction in an iron conductor under the influence of a current passing through 
it. The method of experiment was briefly in this wise. An iron tube was magnetised 
circularly by a current passed from end to end along its entire length ; and the induction 
so produced in the iron was measured in terms of the current induced in a coil of wire 
wound longitudinally round the walls of the tube. 

In the experiments four tubes were used, all of the same length and nearly the same 
external diameter. The internal diameters of one pair were approximately double those 
of the other. The various dimensions are given accurately in the following table, the 
tubes being distinguished as A, B, a, b. Each diameter measurement is the mean of 
eight measurements taken across different diameters. 

Length of Tubes = 3 4 "8 cm. 

T , Diameters in cm. 

Internal. External. 

A, .... 1-031 ±-012 3-022 ±-003 

B, .... 1-050 ±-010 3-027 ±-003 
a, .... 2-036 ±-004 3"022 ± "003 
6, .... 2-052 =f005 3-021 ±'002 

The tubes were all of wrought iron, turned on the lathe and bored. The a tube was 
made at a much later date than the other three. The results given below show that it 
was made out of quite a different specimen of iron. 

To measure the circular magnetisation, four turns of insulated copper wire were 
coiled longitudinally round the walls of the tubes A, B, and b ; and sixteen round a. 

Each tube could be magnetised circularly in two ways : — 

(1) By an axial current passing along a copper wire led through the axis. 

(2) By a sectional current passing longitudinally through the substance or 

wall of the tube. 

It was by a direct comparison of the inductive effects of these two methods of apply- 
ing the magnetising force that the action of the latter was studied. To this end two of 
the tubes were taken and arranged so that the same current could be passed axially or 
sectionally along them. The induced currents produced in the coils were then balanced 
on a galvanometer exactly as in the familiar method for comparing mutual inductances 

VOL. XXXVII. PART I. (NO. 2). C 



8 PROFESSOR CARGILL G. KNOTT ON 

of two pairs of coils. In this way the magnetic induction produced by the " sectional " 
current along, say, the A tube could be directly compared with the magnetic induction 
produced by the " axial " current along the B tube ; and vice versa. 

To complete the investigation it was necessary to know the laws governing the mag- 
netic action of the axial current. At first it seemed sufficient to assume, in accordance 
with the usual view, that the magnetic force due to the axial current was inversely as the 
distance in the iron substance as well as in the air spaces, and that with the currents used 
the value of the force was small enough to warrant us taking the permeability as constant 
throughout the iron. There were hints, however, that these assumptions were not even 
approximate^ true. Accordingly, a series of experiments was undertaken in which the 
circular inductions due to various axial currents were carefully measured. In some experi- 
ments the induced currents were measured on a ballistic galvanometer ; in others the 
induced currents were measured by balancing them against the induced currents produced 
in the secondary of a standard pair of coils in whose primary the axial current was made 
to flow. The results obtained by both methods were in good agreement ; and I give here 
only the one series. It was the last in point of time, and was very carefully carried 
out by Mr Sawada, a graduating student in physics of the Imperial University of Japan. 

The quantity directly measured was the total induction across a radial section of the 
tube. It can obviouslv be written in the form 



/a 
i'~Rdr , 



where I is the length of the tube, a and b the external and internal radii, R the magnetic 

force at a point distant r from the axis, and // the permeability at this point. In general 

// will be a function of R. If, however, // is unity, we know that R has the value 2i/r 

where i is the total current passing axially through the tube. In this case the integral 

gives us what might be called the total " normal induction " across the radial section of 

the tube. Its value is 

a 2 
U log - 2 . 

Dividing by the area of the section, viz., l(a - b), we get the average magnetic force 
influencing the tube. Thus we may calculate what might be called the average permea- 
bility m, where 

„2 r 

fii log 

' b 
or fjih = S3 . 



« 2 r , 

j§- - J /j. Rdr , 



Here S3 is measured experimentally, and b is calculated in terms of the current and the 
known dimensions of the tube. The values of these quantities are given in the following 
table. 



CIRCULAR MAGNETISATIONS IN IRON TUBES. 



Table I. 



Showing the relation between the average magnetic induction (33) in an iron tube 
under the influence of an axial current, and the average magnetic force (h) as it would be 
throughout the region occupied by the iron if the iron were replaced by a substance of 
unit permeability. 



h 


33 


M = S3/h 


h 


33 


/u = 53/b 


•0299 


9-2 


307-9 


1-654 


2251 


1361 


•0475 


14-6 


308-8 


2-068 


3612 


1747 


•0572 


18-6 


326-2 


2-481 


4900 


1975 


•0724 


25-1 


347-2 


2-895 


5688 


1965 


■1046 


39-2 


375-2 


3-308 


6391 


1932 


•1234 


47-8 


387-5 


3-722 


6967 


1872 


•1900 


79-6 


419-2 


4-136 


7377 


1784 


•2157 


949 


440-3 


4-570 


7823 


1720 


•3218 


162-8 


505-7 


4-963 


8276 


1668 


•4136 


213-4 


516-2 


5-377 


8692 


1617 


•4626 


249-0 


538-6 


5-790 


9054 


1564 


•8270 


544-2 


658-0 


6-204 


9452 


1524 


•8493 


577-9 


680-5 


6-617 


9825 


1485 


•241 


1266 


1021 









It should be mentioned that in the tube used, A namely, one ampere of axial current 
corresponds to an average magnetic field of 0*2150. Thus the highest magnetic field 
corresponds to an axial current of fully 30 amperes. In the experiment this highest 
value was attained by using a multiple wire of many insulated strands, and passing a 
moderate current through all in series. 

It is important to notice that with a current of one ampere the field at the internal 
surface of the tube is nearly 0'4 ; and similarly in any case the maximum field acting on 
the iron is about 1*8 times the estimated average field acting over the entire radial 
section. 

The relations existing between the quantities tabulated above are shown graphically 
in the Plate. The induction curve and permeability curve are both shown complete, and 
on a large enough scale to bring out the deviations from smoothness. They are drawn 
through all the points. 

The induction curve is very similar in form to the induction curves obtained when an 
iron rod is longitudinally magnetised. The same may be said in a general way of the 
permeability curve. One particular, however, in which the results differ appreciably 
from results obtained for iron rods and anchor rings is in the comparative values of the 
maximum permeability and the permeability for the smallest field. This smallest 
permeability is remarkably high as compared with the initial permeabilities given, for 
example, by Rowland, Ewing, or Lord Rayleigh. On the other hand, the maximum per- 
meability is comparatively small, falling short of 2000. How far this may be due to the 
form of the iron tube, or to the inaccuracy of the estimate of the average magnetic force, 



10 



PROFESSOR CARGTLL G. KNOTT ON 



it is impossible to say. It is more than probable, however, that it is largely referable to 
the mode in which the magnetisation is applied. 

There is a second particular that appears to be an essential peculiarity ; and that is, 
the way in which the permeability curve begins its ascent. It will be seen from the 
table that the permeability has nearly the same value for fields below 0*05 ; but that 
above this it begins to grow rapidly. It is evident, then, that for axial currents greater 
than half an ampere, we cannot assume a constant permeability throughout the A and B 
tubes. Even for the a and b tubes, for which one ampere gives an estimated average 
field of nearly 0*16, it would be unsafe to assume a constant permeability for stronger 
axial currents than half an ampere. 

It will be seen from the curve that the permeability is almost accurately proportional 
to the magnetic field from a field of about unity up nearly to its maximum. The curious 
hump-like character of the earliest part seems difficult to explain as a result of hetero- 
geneity in the metal. Whatever be its cause, its existence indicates a remarkably rapid 
increase of permeability when first it begins to increase. I am not aware that any like 
peculiarity has been noticed in other magnetic experiments. Permeability curves seem 
always to begin convex to the axis, and not to become concave until the maximum point 
is being approached. 

In the experiments in which the inductions were measured by ballistic swings, the 
swings were taken at make and break of the magnetising current which was passed first 
in one direction then in the other. From the numbers so obtained it was an easy matter 
to calculate the residual magnetism in terms of the total induced magnetism. With an 
axial current varying from 0*25 of an ampere to 4 amperes, and a corresponding average 
field varying from 0'055 to 0"882, it was found that the ratio of the residual magnetism 
to the total induced magnetism varied from 0'05 to 0'20. 

I now proceed to the discussion of the experiments which form the real subject-matter 
of this paper. 

The method as already briefly described was a nul-method. Two tubes were taken 
and subjected to the inductive effect of the same current. This current could be purely 
axial along both tubes, or purely sectional ; or it could be axial along the one and 
sectional along the other. To guard against any confusion, I shall here formally define 
these terms, although the definition is fully implied in what precedes. An Axial Current 
is a current which flows in a wire forming the axis of the tube, but quite insulated from 
it. A Sectional Current is a current flowing through the substance or walls of the tube 
parallel to the axis. 

The following combinations of tubes with currents were tried : — 



B axial 


with A axial. 


B sectional 


)> A „ 


B „ 


„ A sectional. 


B axial 


i) A ,, 


i „ 


„ a axial. 


b sectional 


» * >» 



b sectional with a sectional. 
b axial „ a „ 

a „ „ A axial. 

a sectional „ A „ 
a axial „ A sectional. 



CIRCULAR MAGNETISATIONS IN IRON TUBES. 



11 



The ratios of the inductions in these different pairs, calculated from the resistances 
needed to be inserted in the secondary circuits so as to obtain a balance on the galvano- 
meter, are given in the succeeding table for three different strengths of current. The 
current strengths are given in amperes at the head of each column. The symbols A, B, 
a, b mean the inductions produced by the axial current ; and A', B', a', V the inductions 
produced by the sectional currents. 



Current = 


•49 


1-05 


2-09 


(1) 


BjA 


1-088 


1-0548 


1-0340 


(2) 


B'/A 


•333 


•2960 


•2898 


(3) 


BjA' 


3-60 


3-857 


3-893 


(4) 


B'/A' 


1-122 


1-077 


1-0868 


(5) 


b/a 


1-338 


1-3395 


1-3333 


(6) 


b'/a 


1-556 


•5437 


•533 


(7) 


b/a' 


3-105 


3-303 


3-404 


(8) 


b'/a'.' 


1-325 


1-340 


1-360 


(9) 


a/A 


•2735 


•2536 


•249 


(10) 


a'/A 


•117 




•0974 


(11) 


A'/a 


... 


1-080 


... 



From these the following pairs of same ratios are obtained, and final means taken of 
these pairs. 



Current — 


•49 


1-Q5 


2-09 




1/3 

2/4 

(12) 


A'/A 

J) 


•302 

•298 


•2735 
•2748 


•2663 
•2667 


(means.) 


•3007 


•2739 


•2664 


2/1 

4/3 


B'/B 


•307 
•312 


•2806 
•2793 


•2803 
•2792 


(means.) 


•3087 


•2802 


•2799 


5/7 
6/8 

(13) 


a'/a 
>> 


•431 

•420 


•4054 
•4058 


•392 
•392 


(means.) 


•427 


•4056 


•392 


6/5 

8/7 


b'/b 


•423 
•426 


•4059 
•4057 


•4000 
•3995 


(means.) 


•424 


•4058 


•3999 


9 
10/13 
12/11 


a/A 

» 
■}■> 

J) 


•2735 
•274 


•2536 
•2536 


•2490 

•2485 


(means.) 


•2738 


•2536 


•2488 



12 



PROFESSOR CARGILL G. KNOTT ON 



It will be noticed that the means are not simple arithmetical means. They are 
obtained by weighting the individual values in accordance with the accuracy of the 
experiments on which these values depend. 

Finally, we may calculate the ratio bjB for each current thus : — 



B 



b a 

a ' A 



A_ 
~B 



Collecting, then, all the results that are of importance, we obtain Table II., showing the 
ratios between the sectional and axial inductions in each tube, and also the ratios between 
the axial inductions in the thin-walled and thick-walled tubes. 



Table II. 



Current = 


•49 


1-05 


2-09 


A'/A 


•3007 


•2739 


•2604 


B'/B 


•3087 


•2802 


•2799 


a'/a 


•427 


•4056 


•392 


b'/b 


•424 


•4058 


•3999 


a/A 


•2738 


•2536 


•2488 


b/B 


•3367 


•3220 


•3208 



For a tube of radii a and ft (a>/3) the sectional current i produces (in accordance 
with the usual theory) at any point r a field 

a 2 - ft 2 r • 

If I is the length of the tube, the total sectional induction across a radial section is 

f&'=/lfjL'hdr 

(8 

= ^'( 1_ i ATi lo S-? j2 ) 

where, for simplicity, we assume // to be constant over the section, and where p = a/j3. 
With the same assumption, we find for the total axial induction the expression 

33 = l/ni log p 2 . 

It is advisable to distinguish /a from yJ, since clearly the average magnetic force due 
to a given axial current is greater than the average magnetic force due to a sectional 
current of the same value ; and we have seen above how much the permeability varies 
with the force. 



CIECULAR MAGNETISATIONS IN IRON TUBES. 



13 



In the following table, the various dimensional quantities on which the inductions 
depend are shown for the four tubes : — 



Tube 


2a 


2£ 


log p 2 


p 2 — 1 


1 — r l °gP Z 
jr — 1 


W/l/ii 


A 
B 

a 
b 


3-022 
3-027 
3-022 
3021 


1-031 
1-050, 
2-036 
2-052 


2-1508 

2-1211 

•7898 

•7735 


7-591 
7315 
1-203 
1-168 


•2833 
•2900 
•6565 
•6625 


•7167 
•7100 
•3435 
•3375 



The column headed log p 2 gives the values of 23/Z/n. 

By dividing the numbers in the 33' column by the corresponding numbers in the 35 
column, we obtain the following ratios of the inductions : — 



E. 



A' /A = -3332 ^ 

B'/B = -33±7 ^ 

M , 
a' /a = -4349 ^ 

/" 

b'/b ='4363 £- 

where it must be remembered that the ratio ix'\p. is not necessarily the same in all. 
We also get the following ratios : — 

a/A =-3669 ^1 

b/B =-3647 ^1 
M 2 

where the suffixes are attached to m to show that the permeabilities for the two kinds of 
tubes subject to the same axial current are not necessarily the same. 

In the light of these results we shall now discuss Table II. In the first place, it is 
evident at once that the a tube must differ specifically from the other tubes, being indeed, 
as already noted, of a different kind of iron. A comparison of the b and B ratios leads 
to the immediate conclusion that 

fj, for b tube 

fori? tube = ^^33 for axial current "49 amp. 



= •8830 
= •8800 



1-05 
2-09 



Now the average magnetic field acting within the substance of the tube is, in terms of 
the usual theory, 0'212z for the B tube, and 0'159^ for the b tube ; i being measured in 
amperes. Thus the average fields for the two tubes under influence of the currents given 
above are 

•104, -223, -445 for the B tube, and 
•078, -167, -333 for the b tube. 



14 



PROFESSOR CARGILL G. KNOTT ON 



From Table I. we may readily calculate that these corresponding pairs of magnetising 
forces give for the ratios of the inductions 

•939, -914, -957 

respectively. These are all somewhat higher than the experimental values just given. 
This, however, is not surprising inasmuch as the kinds of iron composing the two tubes 
may differ enough to render the numbers in Table I. not strictly applicable to the b tube. 
And, again, the theory itself that is made use of in estimating the average magnetic force 
and the induction due thereto is admittedly only approximately true. The comparison 
just made seems to show that it is nevertheless a tolerably fair approximation to the 
truth.. 

The ratios of the sectional and axial inductions call next for consideration. At a 
glance we see that the ratios given in Table II. are all less than the corresponding 
multipliers in equations E. This means that // is less than /x in every instance. In a 
general way, it is easy to see that this ought to be so. The fields due to axial and 
sectional currents of the same strength, although they are the same in the region outside 
the tube, have quite different values in the substance of the tube. The field due to the 
axial current increases as we pass inwards to the interior surface ; while that due to the 
sectional current diminishes, and has the value zero at the interior surface. In any case, 
we may estimate the average field by dividing the total normal induction by the radial 
section. The values of the average fields, so estimated for the different tubes, are 
shown in the following table : — 





Average Field due to Current 




Tube. 










•49 


1-05 2 


09 


A 


•1058 


•2268 


4514 


A' 


•0353 


•0756 


1503 


B 


•1049 


•2247 


4473 


B' 


•0350 


■0749 


1491 


a 


•0785 


•1682 


3348 


a' 


•0342 


•0732 


1457 


b 


•0782 


•1675 


3333 


V 


0341 


•0731 


1455 



Now each of these fields has its appropriate permeability ; and by means of Table I. 
we may calculate the permeabilities in the case of Tube A. From Table II. we see that 
Tube B behaves very similarly to Tube A ; and that Tube a, notwithstanding the fact 
that the permeability of its material is comparatively small, behaves almost exactly like 
Tube b. This is significant as showing that the relation between the sectional and axial 
inductions is largely independent of the numerical values of the permeabilities involved. 
Hence we may reasonably discuss the case of the Tubes a and b by applying to them 
the results of Table I. In this discussion we shall take the means of the various values 



CIRCULAR MAGNETISATIONS IN IRON TUBES. 



15 



for the a and b tubes ; but shall leave Tube B out of consideration, since Table I. applies 
directly to Tube A. 

Calculating, then, the permeabilities for the fields due to the several currents, we find 
as follows : — 





Permeabilities due to Current 


Tube. 










•49 


1-05 


2-09 


A 


376 


447 


533 


A' 


308 


350 


400 


ab 


352 


408 


507 


a'b' 


308 


348 


398 



From these we at once obtain the ratios (///ju) for the different currents and tubes. 
These we shall call the calculated ratios ; while the ratios obtained from equations E by 
use of the values of Table II., we shall call the observed ratios. It remains now to com- 
pare these sets of ratios, as in Table III. 



Table III. 



Current 

Strengths in 

Amperes. 


Ratios of Permeabilities of Sectional and Axial Inductions. 


A'jA 


a'b' jab 


Obs. 


Calc. 


Obs. 


Calc. 


•49 
1-05 
2-09 


•902 
•832 
•781 


•819 
•783 
•750 


•978 
•932 
•910 


•874 
•853 

•785 



It will be seen at once that a ready explanation is found for the diminution of the 
ratio of the two inductions as the field is taken stronger. The numbers in the " calculated " 
columns fall off according to much the same law as those in the " observed " columns. In 
all cases, however, the calculated ratios are smaller than the corresponding observed 
ratios. This may be explained in several ways, thus : either the average magnetic field 
acting on the iron is over-estimated for the axial induction or under-estimated for the 
sectional induction ; or the permeability is really greater under the influence of the 
current passing through the iron than it is under the influence of an equal average mag- 
netic field unaccompanied by such a sectional current. 

If the last be the true explanation, then a direct experiment should show an appreci- 
able increase in the axial induction when a current is in addition sent along the iron 
tube. Now, the effect of a sectional current sustained steadily while the axial is being 

VOL. XXXVII. PART I. (NO. 2). D 



16 



CIRCULAR MAGNETISATIONS IN IRON TUBES. 



reversed will be to impart to the tube a mean circular magnetisation of definite 
amount. The induction will not, at reversal of the axial current, oscillate to equal 
amounts on the opposite sides of zero induction. On the contrary, it will oscillate 
about a mean value of definite amount, so that the total induction will be less on one 
side than on the other. In the ballistic method of measuring inductions, however, this 
one-sidedness or bias would not be apparent. But if the explanation suggested above be 
the true one, the induction due to reversal of the axial current should be greater when 
this current is also directed steadily without reversal along the tube. The experiment 
was accordingly tried in January of 1892, not with the tubes investigated above (which 
being in Japan were unfortunately not at my disposal), but with a short tube supplied me 
by Professor Tait, to whom I would here express my thanks for liberty to work in the 
Physical Laboratory of the University of Edinburgh. The tube was 10 cm. long, had an 
external diameter of 4*1 cm., and an internal diameter of 2'7. The average field through- 
out the region occupied by the iron wall is consequently 0122 for one ampere of current 
along the axis. The following are some of the results obtained, the first column giving 
the current in amperes, the second column containing numbers proportional to the induc- 
tion produced by reversal of the axial current, and the third column similar induction 
numbers when the current was in addition sectional but steady : — 



Current in Amperes. 


Axial Induction. 


Pure. 


With Sectional Current. 


3-26 

4-44 

843 

16-85 


29-8 

43-3 

87-3 

194-6 


30 
43 

85-6 
194-5 



There is no evidence here that the sectional current has any distinct effect upon the 
susceptibility. At any rate, what effect is produced is certainly not increase. 

The discrepancy in Table III. is consequently not to be explained in terms of a direct 
effect upon the susceptibility. We must look for the explanation in the other directions 
indicated. That is to say, the ordinary theory of the circular magnetisation of iron under 
the influence of an axial, or a sectional, current does not strictly apply. It will be noticed, 
however, that the discrepancy is not large, amounting only to 7 per cent. To this 
approximation, therefore, we may regard the ordinary theory as holding for sectional 
currents whose current density does not exceed 0*2 ampere per square centimetre. For 
much greater current densities, as when, for example, a fairly strong current passes along 
a thinnish iron wire, nothing can be asserted ; and it is difficult to see how an experi- 
mental investigation into the circular magnetisation of a solid wire could be undertaken. 



Trans Roy. Soc. Edm 1 ",- Vol. XXXVII 
Knott on Circular Magnetisation. 




uoijonpui 



( 17 ) 



III. — On the Number of Dust Particles in the Atmosphere of certain Places in Great 
Britain and on the Continent, with Remarks on the Relation between the Amount 
of Dust and Meteorological Phenomena. By John Aitken, F.R.S. (With. Plate.) 

Part II. 

(Read 4th January 1892. ) 

In a new investigation of this kind it is always desirable to repeat the observations 
under as many conditions as possible. The variables are so many that with a limited 
experience it cannot be expected that the subject will be exhausted, or that the 
conclusions arrived at from early observations will be in all cases confirmed. As an oppor- 
tunity offered in the beginning of 1890 for repeating the tests made the previous year on 
the amount of atmospheric dust at different places on the Continent, it seemed desirable 
that the old ground should be gone over again rather than that the investigation should 
be extended to new areas. The observations made in this country have also been 
confined to the same stations as in 1889 ; and in this paper I intend giving the results 
of a series of tests repeated at the same stations, at about the same dates, but under 
the conditions existing in 1890, as has already been given for 1889 in Part I. of 
this subject. 

At the end of this paper is given a table in which are entered the places where 
observations have been made, the date and hour when the observations were taken, the 
direction and force of the wind, the temperature and humidity of the air, and the trans- 
parency of the atmosphere at the time. It has not been thought necessary to occupy 
space by entering in the table all the observations made at the different places ; only a few 
of them taken at some of the stations are given ; the others being similar and having no 
special interest are omitted. At Hyeres, tests were made from the 26th March to the 3d 
of April 1890. The general result was somewhat similar to that given in the previous 
paper. The highest number observed on Fenouillet was 15,000 per c.c, the wet-bulb 
depression 5°, the result being a very thick haze. The lowest number observed was 725 
per c.c, with a wet-bulb depression of 9*5°. On this occasion the air was very clear, the 
wind being from the S.W. and strong. The other observations made at Hyeres have no 
special interest, and are not entered in the table. At Cannes, observations were made 
on only two days, and the results call for no special remark. 

Observations were made at Mentone from the 11th to the 19th of April. The tests 
were made on a hill about 800 feet high to the N.W. of the town. The number of 
particles varied greatly with the direction of the wind, being as high as 26,000 
when the wind was S.E., i.e., from the direction of Mentone, while the number fell 
to a little over 800 when the wind was northerly, or from the mountains. This does 
not come out in the table, as the directions of the winds entered in the table are the 
directions from which it was blowing at the place of observation ; but as it was situated 

VOL. XXXVII. PART I. (NO. 3). E 



18 MR JOHN AITKEN ON THE NUMBER OF DUST PARTICLES IN THE 

among the hills, with high mountains to the N., the direction was often quite local. 
From an examination of my weather tubes taken at Mentone at the time, I find that 
the true wind on the 14th and 16th was northerly, and not S.E. or E. as observed 
among the hills. 

During the time of the previous observations at Bellagio the weather was always dull 
and the amount of dust great, but on this occasion there were opportunities of testing clear 
air. It will be observed from the table that whenever the wind fell or went southward 
at this station that the number of particles was great ; and, on the other hand, when it 
went northerly, or became strong, the number of particles fell. 

In the later observations I have tried to introduce a more definite measure of the 
clearness of the air than that given in the table in Part I. For this purpose the limit of 
visibility, or the extreme distance at which a mountain could be seen, has been used. If 
there were any mountain sufficiently far away to be just visible, then the distance of that 
mountain was the limit of visibility for the air at the time. At most stations, however, 
mountains are not available at sufficient distance, and the hazing effect on near ones has to 
be estimated, and from this estimate the extreme limit of visibility is calculated. This 
plan, however, is not very satisfactory, as the air is not equally clear in all 
directions, being greatly influenced by the position of the sun. At mid-day, two hills 
equally distant, but one N. and the other S. of the observer, will not look equally 
hazed; the one to the N. always looks much clearer, or, stated generally, there is 
always more haze when looking in the direction of the sun than when looking away from 
it. It is for this reason that the direction of visibility requires to be known as well as 
the distance. 

It will be seen from the Bellagio observations given in the table that with over 6000 
particles, and a depression of the wet bulb of from 5° to 8°, nothing could be seen beyond 
a limit of 15 miles looking in the direction of the sun, though in the opposite direction 
hills could be seen to a much greater distance. On the other hand, when the number 
of particles fell to about 1000, while the humidity remained the same, the air was 
clear, and all hills within range could be seen, and only some haze between the observer 
and hills 1 5 miles distant. The relation between the transparency and the humidity 
of the air, which has been pointed out in Part I., is also clearly seen in these Bellagio 
observations. Increase in the number of particles, if accompanied by constant humidity, is 
in a general way accompanied by a decrease in transparency ; and increase in the humidity 
is also accompanied by a decrease in the transparency if the number of particles remains 
constant — i.e., both dust and humidity tend to decrease transparency. These con- 
clusions can, however, only be looked for in a general way from observations taken at a 
place of this kind, where it is difficult to get air for testing which is free from local 
pollution. 

There are no points of special interest in the Baveno observations, nor in those taken 
at the entrance to the Simplon Pass. There was no bright, clear air while the observations 
were being made ; the quantity of dust was always large and the air thick. The wind 



ATMOSPHERE IN GREAT BRITAIN AND ON THE CONTINENT. 19 

during the period generally blew from inhabited parts, and when it blew from the moun- 
tains it only did so for a short time, and with but little force, so that the accumulated 
impurities were not swept away. It will, however, be observed that the velocity of the 
wind, even though it blew from a polluted direction, had a considerable influence on the 
amount of dust. On the 3rd, 6th, and 9th of May there was much dust in the air 
in the morning, but as the day advanced the wind rose and the number of particles 
became smaller. 

Rigi Kulm Observations. 

Turning now to the observations made in Switzerland, and comparing them with those 
made in 1889, a marked difference in the state of the atmosphere will be noticed. During 
the first visit the weather generally was fine, and the air had the crisp clearness which 
gives that hard outline and crude colouring one generally associates with Swiss scenery ; 
whereas on the present visit the air was remarkably thick and heavy, the weather dull, 
and the mountains loomed through a thick impure atmosphere. From the conclusions 
arrived at in Part I., one would expect that this great difference in the condition 
of the atmosphere on the two occasions would be accompanied by a difference 
in the amount of dust in the air, if the humidity were the same on both occasions. 
On comparing the results given in the tables for the different years, it will be seen that 
there was no marked difference in the humidity ; but it will also be seen that 
the quantity of dust in the atmosphere was much greater during the visit 
in 1890 than during the previous year. In 1889 the highest number of particles 
observed at this station was a little over 2000 per c.c., and this number was observed on 
only one occasion, whereas in 1890, 10,000 particles per c.c. were observed — i.e., the 
highest observed in 1890 was five times greater than the highest of 1889 ; and if 
we compare the condition of the air at the level of the lake, the same contrast is apparent. 
On the previous visit the number of particles at low level ranged from 600 to 3000, 
while during this visit they varied from 1700 to 13,000 per c.c. Speaking roughly, 
there was about four times as much dust in the air during the visit of 1890 as there was 
in 1889, and the air was about four times as thick. 

On my way up the Rigi on the 15th May of 1890 I stopped at Vitznau, at the 
foot of the mountain, to test the air at the level of the lake. From the table it will be 
seen that the number of particles was much greater than in 1889, and that the air was 
very thick. Three tests were made at different times, giving results varying from 10,000 
to 11,750 per c.c. This thick haze was not due to humidity, as the wet bulb was depressed 
10°, so that the air was what we would call very dry. On arriving at the top of the 
mountain, the air at that elevated situation was tested two hours later. It was found 
that here also there was a large quantity of dust, the number of particles being slightly 
over 4000 per c.c, or double the highest number observed in 1889. 

As the air on- this day was in marked contrast to anything seen on the previous visit, 
I shall make a few extracts from my notes on the points which specially attracted my atten- 



20 MR JOHN AITKEN ON THE NUMBER OF DUST PARTICLES IN THE 

tion. On looking downwards to the valleys and lakes, the air was thick and black 
looking. Sometime before sunset the air was so thick to the westwards that the lower 
slopes of Pilatus were scarcely visible. The lake to the south was visible through a thick 
haze ; and the haze was also distinctly seen when the eye w T as turned in a direction at a 
level with the top of the mountain. Between the observer and the mountains it appeared 
as if a veil were hung between him and the distant scenery. 

Sometime before sunset this hazy veil became coloured by the rays, of the setting 
sun, and its upper limit was well defined in the eastern sky at an elevation considerably 
above the highest Alp. At sunset the dusty impurity became still more apparent as the 
earth's shadow crept up its lower edge. The shadowed part looked bluer by contrast 
with the red haze above, and where the upper edge of the veil mingled with the blue of 
the sky, it passed by imperceptible degrees through white, till it was lost in the blue of 
the heavens. 

Although the sun set on this evening in a cloudless sky, it looked more like a 
harvest moon than the orb of day, and was so dull that it could be gazed at without the 
slightest discomfort. Its rays after penetrating the thick air were so feeble that no colour 
effects were seen on the mountains ; as they were not strong enough to give any percep- 
tible direct illumination, while there was much diffused light reflected by the dust-laden 
air. 

The air on the 16th continued much the same as it was on the previous day, only if 
anything thicker in the afternoon. As the wind rose a little on the afternoon of this day, 
its increase may have been one of the reasons for the increase in the number of particles 
observed as the da} 7 advanced. At low levels increase of wind is accompanied by a decrease 
in dust. As a natural sequence, an increase in wind gives rise to an increase in dust 
at high levels. This will be the case at least when the wind begins to blow and mixes 
the lower impure air with the purer air above ; but after the winds have blown for some- 
time, and cleared the lower impurity away, the amount of dust at high levels will fall again. 

During the 17th the wind remained much the same as on the previous two 
days; the same thick pall hung over the lower landscape and veiled the hills in the 
distance, the number of particles remained high, and the air fairly dry. During 
the afternoon the clouds on the distant mountains began to clear away, but 
about 5.30 p.m. a large mass of clouds formed in the S.W. This bank of clouds 
gave rise to a fine thunderstorm, with a good deal of lightning and rain, which passed to 
the W., but did not come near the Rigi. About 6.30 P.M. another fine mass of clouds 
streamed in from the S., filling the sky to the S.E. On the N. also there lay large 
masses of thunder-clouds. The storm-clouds to the E. and W. of the Eigi passed 
northwards, while the lower wind was directly opposite. The sun set on this evening 
amidst grand towering masses of thunder-clouds, which filled the sky in all directions, 
save over the place of observation. By 9 p.m. these clouds had all passed away to the 
N., the wind had fallen, and the stars shone in a clear and tranquil sky. 

The 18th was a day of special interest. The morning opened much the same as the 



ATMOSPHERE IN GREAT BRITAIN AND ON THE CONTINENT. 21 

previous mornings during this visit : the air still had the same thickness, the amount 
of dust was high for the morning, and there was little change in the humidity. Before 
8 a.m., when the first observations were being made, small clouds occasionally formed on 
the S.E. face of the hill and passed over the place of observation. While in these 
clouds, the temperature fell and the humidity increased ; the temperature being 46° 
and the wet-bulb depression about 1°, which was 2° colder than the surrounding air and 
3 '5° less depression of the wet bulb. 

By 10 a.m. the clouds ceased passing over the mountain, but were still forming lower 
down. As the day advanced, clouds began to form on the Alps to the S., and 
these seemed to have their origin in the air coming from the same sources as on the 
previous day ; one mass formed to the S.W. and moved northwards, while another 
mass came streaming over the Alps from the S. and formed a mass in the S.E. 
and spread northwards, while over the Rigi the sky was clear. Both on this occasion 
and on the previous day the formation of the mass of cloud in the E. was particularly 
interesting ; on both occasions it formed in a cloudless sky. It seemed to be caused by 
hot moist air driven up the southern slopes of the Alps by the wind, and appeared to 
come streaming northwards through some opening in the mountains. At first the 
current formed only a long thin cloud, but as the day advanced the current strengthened 
and the little stream gradually grew and expanded as it moved northwards, and rose in 
the air ; and by the time the day was well advanced, it had grown to a mighty mass 
of thunder-cloud, thousands of feet thick, which completely filled the eastern sky. It 
would be difficult to imagine anything grander than this billowy mass of thunder-cloud 
as it moved northwards shining brightly in the sunlight. 

Between 4 and 5 p.m. the clouds to the S.W. had increased considerably. They 
were forming at an elevation very little above the top of the Rigi. About 5 p.m. thunder 
was heard to proceed from this mass. After a time the active area seemed to move east- 
wards, i.e., to the S. of the Rigi. It then went to the S.E., and finally it came 
directly overhead. As this seemed a favourable opportunity for testing the effect of a 
thunderstorm on the amount of dust, observations were at once begun, and as many 
tests taken as possible while the storm lasted. At 6 p.m. there was a marked increase 
in the violence of the storm. Large hailstones fell thickly and with great force while 
the tests were being, made, which made working extremely difficult. So near was the 
storm at this time that the thunder followed close on the flash, and on one occasion no 
perceptible interval was noticed between a very brilliant flash and the deafening crash 
which accompanied it. 

It has often been contended that thunderstorms cause the " turning " of milk and other 
putrefactive actions by some effect they have in bringing about the deposition of living 
organisms floating in the atmosphere. If thunderstorms really have this effect, then we 
would, expect that they would cause the fine dust in the atmosphere to settle also. I 
had long been desirous of testing this point, to see if thunderstorms had really any 
effect on the amount of dust in, the atmosphere, but as yet had but few opportunities, as 



22 MR JOHN AITKEN ON THE NUMBER OF DUST PARTICLES IN THE 

there had been but few storms during the period of these observations. I therefore 
made the most of the opportunity which presented itself while the violent storm of the 
18th was going on. The occasion was a highly favourable one for getting information 
on the effect of the electric discharge on dust, as the observations would be made 
in the very centre of the storm, and in the air in which the lightning discharges were 
taking place ; and I therefore resolved to take the observations that evening, and with as 
much accuracy as the difficult and trying conditions would admit of. 

The observations made on the 17th as well as those of the 18th bear directly on this 
important point, as on both days there was a good deal of thunder and lightning. Now, 
though there was a good deal on the 17th, yet there was no indication of any reduction 
in the amount of dust. It is true that in this case the thunder was somewhat distant, and 
took place in the evening, while the air was not tested till next morning. 

The storm of the 18th, however, is open to none of these objections. From an 
examination of the numbers in the table, one might at first sight be inclined to conclude 
that in this case there was evident proof of the reduction of the dust by the storm. The 
number of particles at mid-day was nearly 4000 per c.c, at 6 p.m. it was still as high as 
3000, but just in the middle of the storm the number suddenly fell to about 800. In my 
notes I find a remark to the effect that the observations made during the storm may not 
be very accurate, owing to the conditions under which they were made. For instance, 
the 6.20 p.m. observations were taken when the storm was near its worst, and had to be 
made in the open, as it was too dark to work under shelter ; and at this time the 
lightning and thunder were excessively near and violent, and the hail came down in 
heavy showers which obscured the lens of the dust-counter, and made accurate counting 
almost impossible. Under these conditions only five tests could be made, of which the 
one given is the average, when a rush had to be made for shelter. The 7 p.m. observa- 
tions may not be correct from the small amount of light at the time. Although I have 
thrown some doubt on these observations from the conditions under which they were 
made, yet, as the number was much the same next morning, there does not seem to be 
any reasonable cause for supposing they are not fairly correct. If there be any error, the 
number may probably be too low owing to some of the drops escaping detection in the 
feeble light at the time. 

But supposing that these observations are correct, and that as low a number as 800 
was observed after the storm, do they prove that the storm, as a thunderstorm, had any 
effect on the amount of dust in the atmosphere ? I think it must be admitted they do 
not. The violent hail-shower falling at the time of the observations would produce a 
downrush of upper air, and displace the impure air on the mountain by a purer air from 
above. The purifying influence of the downrush of air produced by the hail in this case 
was not nearly so great as that observed in a heavy shower of rain on the Eiffel Tower 
recorded in Part I., when the numbers fell from a very high figure to 226 per c.c. The 
purifying influence of such downrushes depends chiefly on the purity of the air in the 
upper region from which the air is carried by the shower. 



ATMOSPHERE IN GREAT BRITAIN AND ON THE CONTINENT. 23 

On the morning of the 19th there was an entire change in the atmosphere ; it was now 
clear and looked very much as it did during the previous visit. All the thickness was 
gone ; there was nothing but a fine haze in all directions. Had anyone been present on 
this morning who was inclined to believe in the dust-clearing effect of thunderstorms, his 
belief would have been much strengthened by the improved and purified appearance of 
the atmosphere after the storm. We have given reasons for supposing that the storm, 
as a thunderstorm, had no influence on the amount of dust, and it will be seen later on 
that the change was not due to any change in the air, but to a change of the air itself. 
The increase in the transparency of the air on this morning was accompanied by a 
reduction in the number of particles, which was now as low as last year. As the day 
advanced the number gradually diminished to about 400 per c.c. The air was fairly dry 
and very clear. Zurich, which is 25 miles distant, was visible, as well as the range of the 
Jura Mountains to the N., while far in the E. was clearly seen Hochgerrach, one of the 
most distant mountains seen from the Rigi, being about 70 miles away. All these were 
seen on this morning for the first time this year. The upper atmosphere remained clear 
during the whole day. It, however, did not remain long in this condition, as next 
morning the air was beginning to thicken, and by mid-day there was a thick haze, and 
the air had much the same appearance it had during the first days of this visit, and the 
number of dust particles was again very great. 

The last of the observations made on the Eigi were taken at mid-day of the 20th, after 
which I proceeded on my way to Lucerne. On arriving at Vitznau, at the foot of the 
mountain, the air was tested at 3 p.m., when it was found to be very impure ; the number 
of particles being as high as 10,250 per c.c, or much the same as it was when tested on 
the way up the mountain. Its humidity was also much the same, and the air had very 
much the same thick appearance. 

I was just completing these observations at Vitznau, and was about to pack up to 
catch the boat for Lucerne, when, on looking over the figures in my note-book, I noticed 
an unusual unsteadiness in the numbers. At first I began to fear something had gone 
wrong with the instrument, and that the observations would require to be rejected. It 
was, therefore, necessary before packing up to test the apparatus. On doing this, no fault 
from leakage or otherwise could be found. There was, therefore, no reason for rejecting 
the observations ; it was, however, thought advisable to repeat the test. When this was 
done, it became evident that the number of particles was becoming still smaller. The 
second test showed that the number had fallen from 10,250 to 6000 per c.c. The 
next test gave only 3500. As usual, all these figures are from averages of ten tests. 
Under these conditions it was difficult to get rid of the feeling that the instrument was 
not working correctly. The rapid fall to about one-third the number of particles did 
not add to my comfort, but again gave rise to unpleasant feelings regarding the value of 
the observations, more especially as the next test showed the number to be now under 
3000 per c.c. Fortunately, my discomforts were soon ended and confidence restored. 
It was now time to take the readings of the wet and dry bulb thermometers, and also 



24 MR JOHN AITKEN ON THE NUMBER OF DUST PARTICLES IN THE 

the hygroscope, which is generally hung alongside the thermometers. It was not a little 
gratifying to find that these instruments also showed the air had entirely changed. The 
temperature had risen 3 degrees since the first test was made, having risen from 71° to 74°. 
But not only had the air risen in temperature, it had also become greatly reduced in 
humidity. The wet bulb was now 3° lower than when the observations were begun, the 
depression having increased from 11° to 17°, showing that the air was not only dryer owing 
to rise of temperature, but that its absolute humidity was much less than at first. It was, 
therefore, evident that some change had taken place by which air from a different source 
was now coming to the place of observation, and that we were now testing quite a different 
air from what was tested at first. On looking into the cause of this change it was found 
that, when the tests were begun, the local wind was light and came from the westwards, 
i.e., off the lake ; but afterwards it had changed first to S.W., then to S.E., and had, at 
the place of observation, greatly increased in force. This rapid change in the direction 
of the lower current seemed to be caused by the upper south-westerly wind striking 
the face of the mountain, which is here nearly vertical in some places, and curving 
^downwards and outwards from the mountain to the lake, and in a direction nearly 
opposite to the true wind. The trees on the face of the mountain were distinctly seen 
bending in the strong wind ; their movements clearly indicated that the air coming to the 
place of observation was upper air, forced down to the level of the lake by the upper 
current meeting the face of the mountain. So long as this circulation was kept up, and 
the air blew down from the mountain side and out to the lake, the number of particles 
tended to get lower, the air also tended to get hotter and dryer, till at last the number 
of particles was as low as 1700 per c.c, or one-sixth of what it was at first; the tem- 
perature had risen about 4 degrees, and the wet bulb was fully 1 8 degrees below the dry. 

About an hour after the observations began it was noticed that the upper S.W. wind, 
which was causing the lower counter-current, was gradually extending downwards. It not 
only struck the mountain face high up, but began to affect the trees very little above the 
level of the lake, and, at last, the counter-current ceased, and the S.W. current extended 
quite down to the lake, and the air again came in off the water. When the wind returned 
to its original direction, the quantity of dust rapidly increased, and became rather larger 
than it was at first. The air rapidly fell in temperature at the same time to rather under 
what it was at the beginning, while it also regained its original humidity. 

These Vitznau observations point an important lesson which one is apt to forget, 
which is this, that in testing the air we are testing the condition of only a thin layer of 
air resting on the ground. The very exceptional and favourable conditions which 
existed for a short time at Vitznau, when the upper air was driven down to the place of 
observation, show how much the upper and lower air may differ as to dust, temperature, 
and vapour. If this be so, it may be objected that all tests of dust as ordinarily made 
are valueless. It must, however, be remembered that almost all our meteorological 
observations are made on the conditions of this same thin layer. If we are to abandon 
all observations because we cannot get perfect conditions for our tests, there would be 



ATMOSPHERE IN GREAT BRITAIN AND ON THE CONTINENT. 25 

an end to all advance. We must, however, always bear in mind that our tests only 
show the condition of a thin stratum of air resting on the ground and tell us little of 
the condition higher up. Even on mountains we do not test the upper air, as the air 
resting on the mountain face is often only the lower air more or less diluted with the 
upper air. It must also be remembered, that though the lower stratum is very different 
from the air immediately over it, yet it is from this lower layer that the upper 
atmosphere receives most of its dust and humidity, and a study of these at their source 
may tell something of their future. 

The Eigi Kulm observations for 1890 show very clearly the ascent of the lower air 
to the mountain top during the day. When the mountain slopes are exposed to radia- 
tion at night, the air resting on them gets cooled, and a downward current is produced. 
This downward current draws its supplies more or less from the pure air above, and the 
air on the mountain top in the morning is pure. But after the sun is up, the mountain 
slopes get heated, the direction of the current is reversed, and the air from the valleys 
drawn to the top of the mountain. The Ben Nevis dust observations show the daily 
variation very well. The large dust-counter fitted in the tower of the Observatory 
enables observations to be made at all hours of the night as well as day ; and by getting 
observations before and after the sun has risen, important information has been obtained 
on this point. An examination of the Rigi observations will show that on all days, 
except the 19th May, the number of particles was lowest in the morning, and that they 
increased as the day advanced. It will be observed that the valley air had generally 
arrived at the top of the mountain by mid-day. Of course, wind and cloud will have 
great influence on this up and down movement, both on its amount and on the hour of 
its arrival at the top. The observations made in 1889 on the Rigi do not show the 
day maximum well, except on the 22d May. The reason for this may have been that 
during the period of the 1889 observations, the lower air was comparatively pure, so 
that though it may have arrived at the top of the mountain it was not recognised, as 
it bore no indication of having passed through the valleys. 

Pilatus Kulm. 
The 21st of May, the day after the Vitznau observations were made, was wet nearly 
the whole day, and the morning of the 2 2d opened dull and cloudy. As a complete 
change had taken place in the weather since the Rigi observations were made, it was 
thought some information might be gained by testing the air in its altered condition at 
a high level. Instead, however, of returning to the Rigi Kulm, Pilatus was selected for 
the purpose. On the way up the mountain, we passed through irregular masses of 
cloud. The first of these were met at an elevation of about 1500 feet, and on the top 
we were surrounded by dense clouds, which continued all day. The wind during the 
visit was extremely light and variable. It looked as if the movements were due to the 
clouds surging up the face of the mountain. They seemed to rise sometimes on one 
side and sometimes on the other. Many tests were made during the day, but it has not 

VOL. XXXVII. PART I. (NO. 3). F 



26 MR JOHN AITKEN ON THE NUMBERS OF DUST PARTICLES IN THE 

been thought necessary to enter them all in the table. As might have been expected 
from the irregularity of the movements of the air, the numbers varied greatly at short 
intervals. The highest number observed was 1275 per c.c., and the lowest 625 per c.c. 

Dust and Wind on the Rigi. 

During the first visit to the Eigi the air was generally clear, whereas during the 
second it was almost always very thick. On looking for an explanation of the greater 
thickness on the second occasion, we may suspect two things, either together or separately, 
as the cause of the increased thickness, — either there was an increase in the humidity or an 
increase in the dust, or an increase in both. The observations show no sufficient increase 
in the humidity to account for it, while the dust observations show a vast increase in 
the number of particles. The question now is, What was the cause of the greater 
number of particles during the second visit ? One naturally expects that the force and 
direction of the wind will have an important influence on the amount of dust. We 
have previously seen that increase of wind reduces the amount of dust at low level. This 
gives rise to an increase at high level when the wind first begins to blow, though after 
it has blown for sometime it causes a decrease of dust at high level also. The direction 
of the wind, however, has an important influence at this station, as all to the north of 
it is densely inhabited, while the Alps close in round it to the south. 

An examination of the air circulation during the two periods has been made from the 
weather charts of Switzerland kindly supplied to me by M. Billwiller. Selecting the 
meteorological stations surrounding the Rigi, an examination was made of the force and 
direction of the winds during the periods to see if there were less wind, or if it blew more 
frequently, from the N., i.e., from polluted areas, in 1890 than in 1889. No satis- 
factory explanation of the difference was obtained from this examination, partly because 
the information about the winds, as regards their force, is too slight, but principally 
because the winds were generally light and variable. And often the direction at one 
station bore no relation to the direction at the others, and at two adjoining stations the 
wind would often be blowing in exactly opposite directions. No satisfactory conclusion 
could, therefore, be drawn from these charts worked in that way. One interesting point, 
however, came out from an examination of the winds during these periods. It was found 
that the wind had a decided tendency to set in towards the S. during the day, and 
from the S. at night — i.e., when the morning observations were taken at 7 a.m. 
the direction was frequently southerly, i.e., from the Alps; and when taken at 1 p.m. 
it had frequently changed to northerly, i.e., to the Alps. One is quite prepared to 
find this up and down movement near mountains, but one would scarcely expect to find 
it takes place over a great part of Switzerland. 

From these remarks it is evident that no satisfactory explanation of the difference on 
the two occasions could be obtained from an examination of the winds at all the stations. 
Another plan was then tried, and the winds of only the high-level stations examined. 
The true explanation was likely to be obtained from them, as they would show the 



ATMOSPHERE IN GREAT BRITAIN AND ON THE CONTINENT. 27 

general circulation of the air, while the low-level stations gave frequently purely local airs. 
The high-level stations near the Eigi area, and suitable for our purpose, are the Santis, 
8215 feet; the St Gothard, 6935 feet; and the Rigi, 5905 feet — using for the latter 
station my own observations, as none are entered in the Swiss Records for this station 
on these dates, the telegraph not being in use till later in the season. 

An examination of the winds at the high-level stations at once showed the cause of 
the difference on the two occasions. During the visit in 1889 the wind was always 
southerly, whereas during the second visit it was frequently northerly. Entering more 
into detail, I find that on the morning of the day I arrived, on the first visit, the wind 
at the St Gothard was blowing strong from the St, and that it continued to blow from 
that direction, and generally with some force, all the days of the visit. At the Santis it 
was generally southerly, but occasionally it went a little E., or W., of S.; while on 
the Rigi it was always E. of S. — i.e., during the first visit the upper wind always came 
from the mountains, and brought pure air to Switzerland. On the occasion of the second 
visit, when the observations were begun on the 15th May, the wind was northerly on 
the St Gothard and the Rigi, and westerly on the Santis. The wind continued in much 
the same direction on the 1 6th at the St Gothard and the Santis, while on the Rigi it 
was southerly but light. On the 17th the wind was still northerly on the Santis and 
Rigi, but showed a tendency to change on the St Gothard, there being a slight southerly 
air by mid-day. During the days of northerly circulation the number of dust particles 
was much greater than in the previous year, when the wind was southerly. During the 
continuance of the N. wind, with its great number of particles, the air remained thickly 
hazed and the hills veiled. The 18th brought a change in the conditions. In the 
morning it was blowing fresh from the S. at the St Gothard, and the wind also had 
changed to southerly on the Santis and Rigi. By mid-day there was only a slight 
reduction in the dust on the Rigi. The impure air seemed to be still passing, but by the 
evening the great impurity brought up by the northerly winds was rapidly being 
cleared away, the dust particles having fallen from a maximum of 3800 to 725. It is 
possible that part of the reduction of the dust may have been due to the heavy hail-shower 
already referred to, but its effect would be only temporary. On the 19th, the wind 
continued to blow from the S. at all the stations, and the number of particles continued 
to fall, and fell quite as low as on the previous year ; the air also became as clear, the 
distant mountains being quite as distinct as on the previous visit. It seems, therefore, 
probable that the clearing of the air was not due to the thunderstorm which took place on 
the 18th, but to the change of wind bringing purer air from the unpolluted area of the Alps. 
It is interesting to note that on this occasion the thunderstorm took place where the con- 
tending pure and impure currents met. So long as the storm was to windward, the number 
of particles was high ; but in the immediate rear of the storm the air was pure. 

On the morning of the 20th the number of particles showed a decided tendency to 
increase, and was very high by mid-day. The wind on the St Gothard was still 
southerly; on the Santis it was S. W.; and on the Rigi, E. But while the upper current 



28 MR JOHN AITKEN ON THE NUMBER OF DUST PARTICLES IN THE 

was mostly southerly, the circulation was a little confused, the winds on the Santis and 
Rigi being nearly opposed. The upper circulation was evidentty weakening, while at the 
lower stations north of the Rigi the winds had set in from the N., and at some stations 
were blowing with considerable force. 

This impure northerly air would seem to have penetrated some distance into the 
northern valleys of the Alps, and been turned over by the upper southerly currents. 
Judging from the number of particles, the upper fold of this current would be as high as 
the top of the Rigi. This folding over of a contrary lower current by an upper one has 
been frequently observed, both with the dust-counter and by actual observation. On one 
occasion it was seen very clearly on the Rigi, when the upper wind was from the S. and 
the lower one from the N. The northerly air low down penetrated some distance into 
the valleys, where it rose on the mountain slopes and curved upwards. This air being 
nearly saturated, as it rose on the mountain slopes it condensed much of its moisture, 
forming a cloud which revealed the directions of its movements. The advanced and upper 
part of the cloud rose, and was caught by the southerly wind and carried northwards again. 
If anyone had been testing in that southerly current at the top of the cloud, he would 
have been testing not southerly but northerly air. A similar condition of matters seems 
to have prevailed on the 20th. The lower impure northerly wind forced its way into the 
valleys of the Alps, where it rose on the mountain slopes into the region of the upper 
current, and was carried by it in the opposite direction. When the air at low level was 
tested on the afternoon of this day it also was found to be very impure. 

Kingairloch Observations. 

The next observations entered in the table are those taken at Kingairloch about the 
same time of the year as the observations given in Part I. The first thing that strikes 
one on looking over the table for 1890 is, that the number of dust particles fell very 
low on a number of occasions, the lowest being much lower than anything observed in 
the previous year. Indeed, the lowest numbers are much lower than any given in any 
previous table, and are the lowest yet observed at any low-level station. Associated with 
this low number of dust particles was a low temperature, as will be seen by a comparison 
of the temperatures given in the tables. The weather on the two occasions showed a 
marked contrast. During the first visit the weather was warm, bright, and sunny ; whilst 
the July of 1890 will long be remembered as one of the worst experienced for many 
years, being cold, wet, and windy. 

During the time I was working at the low level, Mr Rankin was taking observations 
at the Observatory on Ben Nevis as frequently as his many other duties permitted. Ben 
Nevis is situated in a north-easterly direction from Kingairloch, at a distance of about 28 
miles. The two stations are not as close as is desirable, but Kingairloch possesses the 
advantage of being situated in a less locally polluted area than most places nearer the 
foot of the Ben. 



ATMOSPHERE IN GREAT BRITAIN AND ON THE CONTINENT. 29 

Before going further, I wish to call attention to a few of these Kingairloch observations 
that are so exceptional that it is difficult to put a value on them. It will be noticed that 
on the afternoons of many of the days the numbers, which had been low in the morning, 
became very great. When the afternoon observations of July, made on the 3rd, 4th, 6th, 
7th, 11th, and 15th, are examined, it will be seen that the numbers were much higher than 
they were in the morning ; also that they were very high for the direction of the wind. 
All previous experience has shown that winds from uninhabited districts are pure. 
These afternoon observations, however, stand out as marked exceptions to this rule. 

It cannot be said that any very satisfactory explanation has been found of these 
abnormal readings, though the following considerations show how they may possibly be 
accounted for. For the purpose of studying these Ben Nevis and Kingairloch observa- 
tions, the diagram given with this paper has been prepared. In the diagram are entered 
the dust observations taken at both stations from the 1st to the 28th July. The observa- 
tions taken on Ben Nevis were made by Mr Eankin, a copy being kindly supplied to 
me by the Scottish Meteorological Office. Each observation is represented in the 
diagram by a black spot, and the successive observations are connected by straight 
lines. The Kingairloch observations are represented by large spots and connected 
by thick lines, while the Ben Nevis observations are represented by smaller spots and 
connected by finer lines. These irregular lines may, for convenience, be called dust 
curves, and their rise and fall indicate the variations, from time to time, in the amount of 
dust at the two stations. 

At the top of the diagram is entered a series of arrows representing the direction and 
force of the winds on Ben Nevis at the hours the observations were made ; and at the 
bottom another series of arrows representing the winds at Kingairloch. Then, as the 
amount of dust at these stations would probably depend on the general circulation of the 
air over the area of the British Isles, a study of this was made from the weather charts 
kindly supplied to me by Mr Scott of the Meteorological Office, London. The result of 
this investigation is given in the diagram, being shown by a third series of arrows. The 
series of arrows indicating the general circulation are placed between the upper series 
indicating the Ben Nevis winds, and the lower series showing the Kingairloch winds. If 
the general circulation was regular over one area, and the winds blew in one direction at 
all places, then one arrow is sufficient to represent the conditions ; but when the circula- 
tion is mixed, blowing from one direction at one place, and from another direction or 
directions at other places, then two or more arrows are required. By examining this 
series of arrows for any date, it is at once seen whether at the time the general air cir- 
culation was regular or irregular over one area. 

Further, on examining the meteorological weather charts it is seen that, whenever the 
isobars were wide and irregular, the winds were various and variable, and that they blew 
with but little force. On considering what the effect of these conditions would be, it seems 
probable that on the days when the general circulation is confused and light, we cannot be 
certain of the source of the air we are testing ; while we are working in a northerly wind 



30 MR JOHN AITKEN ON THE NUMBER OF DUST PARTICLES IN THE 

it may really be southern air we are testing. This seems to offer a possible explanation 
of the abnormal readings referred to, as the middle series of arrows in our diagram shows 
that the circulation over the British Isles was confused on the 1st, 2nd, 3rd, 4th, 7th, 
8th, 11th, 15th, 16th, 17th, 18th, and 26th. It will be noticed that these dates cover 
most of the days on which the abnormal readings were got. When the general air 
circulation is in a confused condition, we cannot expect the same uniformity in the air as 
when it is regular. As might be expected, abnormal readings were not got on all days, 
nor during the whole of the days, on which the circulation was mixed. It may, however, 
be mentioned that the observations on Ben Nevis support this explanation, as on 1st, 
2nd, 3rd, 4th, 6th, 8th, 11th, 25th, and 26th, the numbers were high at the Observa- 
tory at some time of the day. With one exception, these are all days on which the 
circulation was irregular. 

There is, however, another explanation possible. An examination of the weather 
charts shows that all these abnormal readings were got after a certain distribution of 
pressure and circulation. Whenever a low-pressure area appeared over our islands, and if 
its centre passed to the S. of this station when it had moved to a position to the 
S.E. or E. of Ben Nevis, the numbers went high with northerly winds during some 
period of the day. When a cyclone moves along this route, the effect is to give rise, 
while it is approaching our area, to south-westerly winds over France and Belgium. 
This drives the impure continental air to the N.E. Then as the centre of depres- 
sion advances, this air is driven northwards ; and when the centre of the cyclone lies to 
the E. of this station, the air which moved northwards curves round and arrives at our 
station from a northerly direction. By this explanation, the impurity of these northerly 
winds was not due to contamination acquired in our area, but was due to impure con- 
tinental air which had been driven northwards over the North Sea, and had curved round 
and come to the station as a northerly wind. This explanation would account for the 
high readings got on the 6th, when the general circulation was regular, and the wind 
was from the N.W. 

The irregular circulation within our own area, or the circulation northwards of con- 
tinental air, may or may not be the cause of these abnormal readings. These explana- 
tions are offered at present for want of better, though one or other, or both, may possibly 
be true ; yet the evidence is far from conclusive. It would be difficult, by studying 
the weather charts, to trace the different masses of air on these days from the place of 
observation to their sources. 

Dust and Wind at Kingairloch. 

The effect of the direction of the wind is very evident in these Kingairloch observa- 
tions. It should be mentioned that winds from S. to E. at this station bring the most 
polluted air, being from the most densely inhabited district, while winds from S.W. 
to N. blow from the least inhabited areas. From the table and the diagram it will be 
seen that from the afternoon of the 2nd to the afternoon of the 10th, with the exception 



ATMOSPHERE IN GREAT BRITAIN AND ON THE CONTINENT. 31 

of the abnormal afternoon readings already referred to, the amount of dust was small, 
and wind northerly or westerly. On the 11th the number was high at both upper and 
lower stations, owing to the general circulation being light and irregular. On the morn- 
ing of the 12th the number of particles was still very high, but before mid-day the wind 
went to the W. of S. and cleared away the dust. The wind remained westerly 
during the 1 3th, 1 4th, and morning of the 1 5th, and during these days the dust remained 
very low. On the afternoon of the 1 5th the circulation became irregular, and the number 
of particles great. On the 16th there was much dust in the air, partly owing to a mixed 
air circulation and partly to the wind being E. of S. The wind changed on the after- 
noon of the 16th to N.W., and the amount of dust fell greatly. On the morning of the 
17th the S. wind was again blowing in the early morning, and the amount of dust had 
increased, but it again fell in the afternoon under the influence of a N.W. wind. On the 
18th there was little dust, and the circulation was slight from the N. The wind on 
the 19th changed to E., and the dust increased greatly, but fell on the 20th, and remained 
low till the 25th, owing to a N.W. wind which blew during all these days. On the 
afternoon of the 25th the dust rose under the influence of a S.E. wind, but fell on the 
following day, when the wind went W., but rose again on the 27th owing to easterly 
wind, and fell on the 28th, the air on that day coming from a westerly direction. These 
results confirm the conclusions arrived at in Part I. 

During the time these observations were being made at Kingairloch, the weather was 
frequently disturbed by depressions which passed across the United Kingdom, and gave 
rise to very unsettled conditions ; but on the 20 th an anticyclone approached our 
islands from the W., and the conditions remained fairly steady till the afternoon of the 
25th. During all these days the isobars were regular, and kept their direction constant, 
and the wind blew steadily from the same point. From an inspection of the table and 
diagram it will be seen that the wind on these days blew steadily from the N.W. This 
N.W. wind rapidly swept the impure air away, and during the five and a half days it 
blew the number of particles was very low, — on two days excessively low, — and remained 
low till the direction of the wind changed. 

A comparison of the number of particles at low level at Kingairloch and on Ben Nevis 
shows that though there is considerable resemblance in the figures at the two stations, yet 
the likeness is not very close (see diagram). We could not expect otherwise, as the con- 
ditions are so different at the two stations. The day maximum of dust on most days at 
high level interferes greatly with the parallelism of the two sets of observations. Further, 
the effects of the force of the wind on the number of particles is not the same at high 
and low level ; and, again, the winds are often different at the two stations. As a 
rule, however, when the numbers were high at the low level they were also high on the 
Ben, and when low at low level they were low on the Ben. On the 1st, 2nd, 3rd, 4th, 
11th, 12th, 19th, 25th, and 26th, the numbers were high at Kingairloch, and on the Ben 
they were also high. On the 5th, 7th, 10th, 20th, 21st, 22nd, 23rd, 24th, and morning 
of 25th, they were low at both stations. Between the 12th and 18th only two high- 



3*2 MR JOHN AITKEN ON THE NUMBER OF DUST PARTICLES IN THE 

level observations were taken, so that for this interesting period no comparisons can be 
made. As a rule, the number at the high level was less than at the low one, but there 
were exceptions to this. For instance, on the morning of the 4th the number was much 
greater on the Ben than low down. This was owing to the upper station being in a N.E. 
wind, while the lower one was in a purer N.W. one. Again, on the 24th, under the 
influence of an easterly wind, the number at the high station was greater than was observed 
in a N.W. wind at the low station. This tendency of the number to rise at the upper 
station with easterly winds is also shown in the numbers for other days. For instance, 
the numbers during the night of the 22nd rose with an E. wind from 225 to 550, and 
the number which was about 200 on the 25th rose during that night to 1500 by the 
wind chancrinsj from N. to S.S.E. 

As the observations taken from the 19th to the 25th illustrate the effect of the 
wind on the distribution of the dust at the two stations, we shall here consider them 
more in detail. On the 19th, when there were variable light airs, the number of particles 
was occasionally very high at both upper and lower stations. But a change took place 
in the wind next day. At 1.30 a.m., when the first observation was made at the high 
level on the morning of the 20th, a N.N.W. wind had begun to blow, and had swept 
away the impurities of the previous day, the number having fallen from 2200 to 
562 per c.c. ; and the number remained about 500 till 6 a.m., when the observations were 
stopped, and were not resumed till near midnight. When the observations were begun 
at low level on the morning of the same day, i.e., the 20th, the number was almost 
exactly the same as it was in early morning at the high level being a very little under 
500. During the whole of this day the air remained about the same degree of purity at 
the low level. When work was resumed about midnight at high level the number was 
very low, as low as 10 per c.c. Early on the following morning, i.e., on the 21st, the 
number was excessively low at high level, being only 2 per c.c. at 4 a.m., and the number 
remained very low all day, the day maximum being about 200. At low level the number 
was also found to have fallen very low. When testing began in the morning the number 
was occasionally under 50 per c.c, and the maximum during the day only 180. Next 
day the numbers remained very low at both stations, though not quite so low as on the 
previous day. On the 23rd matters continued in much the same condition, the wind 
was still blowing strong from the N.W., and extremely low numbers were observed at 
both stations. Less than 40 per c.c. was twice observed at the high level, whilst under 
20 was observed at the low one. The maximum at neither station got much over 250 
during the whole day. On the 24th the number was under 50 at the high level in early 
morning, but as the day advanced the number rose to 675, under the influence of the 
day maximum and change of wind to the E. ; whilst at the low station the numbers 
never rose over 210, owing to the N.W. wind continuing to blow all day at that level. 
The numbers which were large during the day at the upper station fell to 200 during 
the night, under the influence of a northerly wind. At 10 a.m. on the morning of the 
25th the number of particles at both stations was about 200, and the wind at low level , 



ATMOSPHERE IN GREAT BRITAIN AND ON THE CONTINENT. 33 

was still northerly, while at high level it had just ceased to blow. About mid-day it 
had changed to S. high up, and to S. and then to S.E. low down, and the dust at both 
stations had begun to rise. At 12 o'clock it was 450 at the high station, while at 
the low station it had risen from 203 at 10 a.m. to 1325 at 3 p.m., and 2200 at 6 p.m. 
At high level also the number continued to rise after mid-day, and was over 1000 
at 10 p.m., and continued rising till a little after 1 a.m. on the following morning, 
when the number was 1500 per c.c. At midnight the wind had greatly increased 
in strength, and was blowing with a force of 3, and had backed to S.S.E. After 2 a.m. 
on the 26th the number at high level had greatly decreased under the influence of 
the strong wind, which had still further increased and swept away the impure air. As 
the morning advanced the wind changed to S.W., and in the afternoon it had gone 
N. W. and fallen in force to 1 to 2. With these changes the number of particles fell from 
1500 to 175 per c.c. 

While all these changes were taking place on the 26th at the high level, matters were 
somewhat different at the low one. The wind, which was S.E., had changed to S.W. by 7 
a.m. at the high station, and the number of particles had fallen ; but at the low station the 
wind was still S.E., or the same as it was the previous night, and the number of particles 
was still high, being 1950, or very near what it was the previous evening. When the 1 
p.m. observations were made at low level the wind was found to have changed to the W., 
with the result that the number of particles was now low at the low station also. The 
number fell to 35 per c.c, which was much lower than was observed at high level on this 
day. On the following day, the 27th, the wind went southerly at both stations, and the 
dust increased to 1950 at the low station and 662 at the high. The following day the 
wind was westerly at both stations, and the amount of dust fell at both. 

While these high and low level observations were being made, a record of maximum 
and minimum temperature was kept at the low level. Observations were also made on 
the solar and terrestrial radiation by means of a thermometer with black bulb in vacuo, 
and a minimum thermometer placed on the grass. These observations were kept with the 
view of seeing whether the dust in the atmosphere has any effect on the temperature 
of the air and on the radiation, as previous observations seemed to indicate. 
Unfortunately, owing to the climatic conditions during the period, — there being no 
days of continuous sunshine nor nights without clouds, — these radiation records are of 
no value, as the temperature of the air during the period was more a question of the 
direction and force of the wind than of local influence. 

Dust and Transparency. 

During these Kingairloch observations an attempt was made to measure more 
accurately the transparency of the air in the manner described in previous parts of this 
paper, by estimating the amount of haze on the distant mountains. This was done with 
a view of testing more closely the relation' between the amount of dust in the air and its 
transparency. In order to prevent any mental bias, from a knowledge of the number of 

VOL. XXXVII. PART I. (NO. 3). G 



34 MR JOHN AITKEN UN THE NUMBER OF DUST PARTICLES IN THE 

particles actually present, the estimates of clearness were always made before the 
dust, temperature, and humidity readings were taken, and were entered in the field note- 
book along with the direction and force of the wind. The clearness was measured by 
estimating the amount to which a mountain was hazed. Then, knowing the distance of 
the mountain selected, it is easy to calculate the extreme limit of visibility of that particular 
sample of air. For instance, if the hill selected were 20 miles distant, and half hazed, 
then 40 miles would be the extreme limit of visibility of the air at the time. In this way 
all the observations can be reduced to one scale for comparison. It should be stated that 
at Kingairloch all observations of this kind bad to be done in a south-easterly direction, 
as only in this direction could distant hills be seen. In the other directions the view 
was closed in by mountains only a few miles distant. 

In working out these observations on the haze they were divided into sets, and 
arranged in tables according to the humidity of the air at the time, for the reason already 
given in Part I., — all the observations taken when the wet-bulb depression was 4° being 
entered in one table, all those taken while it was 5° in another, and so on. (When the 
wet-bulb depression is less than 4° the real humidity is frequently uncertain, because 
when the depression is slight it is generally after rain, and the wet-bulb depression is 
thus very much influenced by local conditions, such as wet ground, trees, &c.) The 
observations in the different tables were then rearranged, — the observation which has 
the greatest number of particles being put at the top of the column, then the next 
greatest, and so on, down to the observation which has the fewest particles. Then 
as the humidity of all the observations in each table is about the same, the limit of 
visibility of the observations at the top of the table ought to be the least, as at this end 
of the column there is most dust, and the limit of visibility should increase towards the 
foot of the column, and be greatest in the last entered observation. 

When this is done and all doubtful dust observations are rejected, as well as all 
observations taken in or immediately after rain, on account of the uncertainty of the 
value of the humidity readings taken under the conditions, it is found that in the tables 
for depressions of 4°, 5°, and 6°, the order of the limit of visibility is, in a general way, 
inversely as the number of particles. In all three tables the lowest limit is associated 
with the greatest amount of dust, and the widest limit with the least. There is, how- 
ever, some mixing of the relative positions of the intermediate numbers, as might be 
expected. 

The results obtained by this method of working are not so satisfactory when we 
come to test the effect of the dust in very dry air, such as that giving depressions of 7° 
and more. In the tables for high depressions the figures for the limit of visibility are 
very much mixed, large numbers appearing near the top of the column as well as near the 
foot. There are many reasons for this. One is the conditions under which the estimates 
of haze have to be made. When the air is very dry, it is clear with even much dust in 
it. All estimates have, therefore, to be made on a thin haze, as seen on distant and high 
mountains, and it is difficult to estimate a thin haze. And, further, as these estimates 



ATMOSPHERE IN GREAT BRITAIN AND ON THE CONTINENT. 35 

have to be made on the hazing of high mountains, they have, therefore, always to be 
made on a good deal of upper air, which may vary greatly from the air tested at low 
level. Further, there is a fundamental error in this method of estimating haze which 
was not observed till after the observations had been made. As we have said, when the 
air is clear the haze on some distant mountain has to be estimated. And in making 
this estimate one compares the whiteness of the haze on the mountain with the whiteness 
or brightness of the background, which in this case is the sky. Now, it is evident that 
if the sky be full of white clouds, and. the background bright, it will require far more 
haze to make the mountain invisible than if the background were darker. Again, 
suppose there are no clouds and the background is only haze, and suppose the con- 
dition to be such that the mountain seems half lost in haze. If we were now to double 
that haze, the mountain would not become invisible, because whilst the air between us 
and the mountain has been thickened, the brilliancy of the background, against which we 
see^ the mountain, has also been; increased. If the brilliancy of the background were 
doubled, the mountain would still be only half hazed ; but, of course, double hazing 
will give less than double brilliancy to the background. It seems to be for these 
reasons that the estimates for clearness in dry air do not show the hazing effect of the 
number of particles in the same way as when the air is damper, and the estimates of 
haze are made on lower and nearer mountains, and, therefore, more in the air: tested. 
The estimates of haze when the air is dry being of no value, they have not been 
entered in the table. It is evident from these remarks that a , more accurate method 
of measuring haze is required. 

In the Appendix to Part I., when discussing some observations made during a gale 
of wind, it is pointed out that high winds will probably have the effect of making the 
air look thick for the number of particles and the humidity. This conclusion is con- 
firmed by the observations in the table given with this paper. In all the observations 
taken while, or immediately after, the wind was high, the transparency was very low for 
the number of particles and the humidity. As will be seen from the table, on the 9th, 
22ndj and 24th July, the wind was high and the transparency very low for the other con- 
ditions. On some other days the transparency was also low for the dust and humidity, 
but on these days the thickening was due to passing showers. The hazing effect of high 
winds would seem to be due to the air carrying large particles, such as dust from roads, 
&c, and also to the wind mixing impure lower air with the upper. Part of the hazing 
may also be due to the unequal densities of the -mixed airs. 

Alford. 

At this station both* purer and less pure air was observed in 1890 than in 1889. As 
will be seen from the figures, in the tables, the purest observed in 1889 had about 500 
particles per c.c, whereas in 1890 under 200 per c.c. was observed on three occasions. 
During last visit the maximum; was 5700, while on this visit it was 6800 per c.c. _j 



36 MR JOHN AITKEN ON THE NUMBER OF DUST PARTICLES IN THE 

Dust and Wind at Alford. 

In examining into the cause of the fluctuations in the number of particles at Alford 
as given in this year's observations, it is at once seen that, here also, the direction of the 
wind is the principal agent in producing the changes. With the exception of the 8th 
September, on all days when the wind was W. or N.W. the number of particles was small 
and the air clear, and when the wind went southerly the numbers became great. 

As the meteorological conditions remained very constant during most of the time 
while these Alford observations were being taken, we shall describe somewhat fully the 
conditions prevailing during the period. An examination of the weather charts shows 
that when these observations began, the weather over our area was very much governed 
by anticy clonic conditions. During the beginning of the month an anticyclone lay to 
the S. of our area, and the centre of high pressure had moved in a north-easterly 
direction, and lay off the S.E. coast of England on the evening of the 7th. The 
winds on this day were southerly over most of our area, and the air at our station was 
impure air from inhabited districts. On the 8th, the day when the testing began, the 
centre of the anticyclone began to move westwards. This caused a change in the 
direction of the winds, making them more westerly over most of our area ; but the wind 
was light, and, as the figures in the table show, it had not yet cleared away the impure 
southerly air, as the amount of dust was great. On the 9th the centre of the anti- 
cyclone had moved still further W. , and the winds over our area were now all westerly ; 
and, as will be seen from the table, the pure westerly air had displaced the southerly air, 
the number of particles having fallen greatly. On the 10th and 11th the centre of 
the anticyclone still lay to the S.W. of our islands. The wind, therefore, continued 
to blow from a westerly direction, and the air remained pure. On the 12th the anti- 
cyclone again approached our islands, and its centre was over the Irish Sea. The wind 
was, however, westerly at our station, and, being from the direction of the Atlantic, it was 
still pure. On the 13th, however, the centre of high pressure continued to move east- 
wards, and now lay to the S.E. of our station, near where it was on the 7th, and a 
corresponding change took place in the circulation. The air no longer came in from the 
direction of the Atlantic, but from the inhabited parts of our islands ; the position of 
the anticyclone giving rise to southerly winds at our station. During the rest of the 
time the anticyclone remained fairly constant, moving about a little, generally in an 
easterly direction ; but even so late as the 23rd its centre still lay over Western 
Europe. 

On the 15th a depression approached our islands from the W. and moved N.W. 
outside our area. As the area of high pressure was at this date situated to the E., 
the isobars were all parallel and regular, but their direction was N. and S., i.e., 
for southerly winds at our station. Under this distribution of pressure the polluted air of 
the inhabited parts of England and Scotland was carried to our station, and the number 
of dust particles observed was high while the cyclone passed. 



ATMOSPHERE OF GREAT BRITAIN AND ON THE CONTINENT. 37 

Another depression appeared in our area on the 19th. On that day its centre lay to 
the S.W. of Ireland. This cyclone moved in a northerly direction, with its centre just 
touching our extreme western coast. As the high -pressure area remained firm in the E. 
at this date, this second depression, like the first, gave rise to regular and somewhat close 
isobars ; but as their direction was again N. and S., southerly winds prevailed over our 
area, and continued to bring impure air to our station, as,, it will be seen, the number of 
particles remained high. Our station did not get free from this distribution of pressure till 
after the observations were stopped, and the amount of dust remained high to the end of 
the observations. 

Callievar. 

As on the previous visit to Alford, an ascent of Callievar was made in 1890 also. 
The morning of the 22nd being fine it was selected for the purpose. At low level the 
number of particles was high, and the wind slight and from the S. On arriving at 
the top of the mountain the view was in striking contrast to what it was the previous year, 
though the weather on both occasions was much the same. On the first visit the Cairngorms 
and Lochnagar were quite distinct, though seen through some haze ; and the number of 
particles was 262 at mid-day, and rose to 475 two hours later. In contrast with this, on the 
second visit the air was thick and densely hazed, only a slight outline of the Cairngorms 
being occasionally detected, while Lochnagar was quite invisible during the whole time. 
The number of particles was 710 at 12.30 p.m., and rose to 1575 two hours later — i.e., 
there were about three times as many particles at the time of the second visit as there 
were at the time of the first, and there was a correspondingly thicker atmosphere. ■ 

Not only was the air much thicker on the second visit, but it also seemed to vary in 
clearness in different directions and at different times. It looked as if the air w T as of 
very different constitution, i.e., came from different sources, at its different parts. When 
the second test was made at 2 p.m., the number of particles had greatly increased from 
what it was at first, and the air had also got thicker. It was also observed that the air 
was still thickening. Tests were, therefore, made at intervals, and from the table it will be 
seen that the number rose to 1575 at 2.30 p.m. A little before this hour it was noticed that 
the air was thicker than it had been half an hour before. At 3 p.m. the air to the W. was 
again clearing, while to the E. it had got much thicker, and the limit of visibility in that 
direction was much reduced. On testing the air at 3 p.m. it was found to be much purer, 
the number having fallen to 1050. 

These observations show that between 2 p.m. and 2.30 p.m. a mass of impure air was 
approaching from the west. This impure air thickened the atmosphere to the west and 
caused the number of particles to rise at the place of observation. This mass of impure air 
drifted across the mountain and passed to the east, after which the air to the west cleared 
and the numbers fell, but the impure air in its passage eastwards thickened the atmos- 
phere in that direction. My reason for entering so fully into these Callievar observations is 
that the conditions were such as to give an opportunity of testing the hazing effect of 



38 MR JOHN AITKEN ON THE NUMBER OF DUST PARTICLES IN THE 

dust under favourable conditions. The observations were all made in a short time, and 
under the same conditions of cloud, sunshine, and humidity. It will be seen from the 
table that the humidity remained fairly constant during the whole time, so that the 
thickness of the mass of air which obscured the atmosphere in the W. between 1.30 and 
2.30 p.m., and which passed over the mountain about 2.30 p.m., and afterwards thickened 
the air to the E., was due to an increase in dust particles and not to humidity. 

On searching into the cause of the want of uniformity in- the air on this occasion, it 
seems possible it may have been due to the influence of the cyclone which was passing to 
the W. of our islands at the time. On the morning of the day the Callievar observa- 
tions were made the centre of the depression lay very near, being on the coast of Scot- 
land immediately to the west of the place of observation, so that there would be at the 
time a considerable difference in the directions of the winds over the immediate neigh- 
bourhood. There would, consequently, be a considerable mixing of airs from different 
places. 

From the tables it might be thought that the great difference in the clearness of the 
air on the occasion of the two visits to Callievar was due to difference of humidity, as 
the figures seem to indicate that the air was much drier during the first than during 
the second visit. The figures in the tables, however, give no information on this point, 
because the wet-bulb depressions for Alford, given in the table in Part I., are maximum 
depressions for the day, calculated from the observations made at Logie Coldstone, one of 
the Scottish Meteorological Stations situated in the same district, whereas the wet-bulb 
depressions in the table in this paper are from observations made at the hours stated, and 
on the mountain. The Logie Coldstone observations for 1890, however, do show that 
the air in that year was not quite so dry as in 1889. The morning observations of the 
day of this visit show 1 *4° less depression than the morning of the last, and the evening 
observations 2*5° less, so that part of the greater thickness in 1890 may have been, due 
to greater humidity. 

GarelocJihead Observations. 

February of 1891 will be remembered in Scotland as having been an unusually fine 
February, fine though that month often is. The temperature was much above the average, 
while the rainfall was much below it. Temperatures between 50° and 60° were frequently 
recorded in our area, and even up to 64° was observed at more places than one. As the 
weather continued very fine towards the end of the month, the opportunity seemed a 
favourable one for testing the amount of dust in: the atmosphere, while we had this 
settled and exceptional weather. For this purpose I went to Garelochhead in the end of 
the month, and was just in time to test the air before the meteorological conditions 
changed, and brought about a state of matters such that the March which followed the 
fine February will long be remembered as one of the coldest experienced in Scotland. 

As will be seen from the table, the number of particles was very large and the air 
excessively thick when it was tested on the 27th of February. The smallest number 



ATMOSPHERE OF GREAT BRITAIN AND ON THE CONTINENT. 39 

observed this day was 7250, while other observations gave nearly 10,000. On the previous 
visit the highest number was 2360 ; this, however, was the only occasion when it was over 
1000. From the table it will be seen that on the 28th the conditions began to change, 
the amount of dust having fallen considerably. The conditions continued to improve, 
and by the 2nd of March the number of particles fell exceedingly low, and remained low 
till the 5th, when the observations were stopped. 

On enquiring into the cause of the great amount of dust in the air in the end of February, 
the meteorological weather charts gave the same explanation as has already been given of 
the impure state of the air during the latter part of the last visit to Alford. For many days 
before the 27th of February the climate of our islands was under the influence of an anti- 
cyclone, the centre of which moved about over Europe, and gave rise to southerly winds 
over our area. These winds brought the impure air of the Continent and England to the 
place of observation. On the 27th the winds were still southerly and light over our area, 
with a confused circulation, and the amount of dust was great and the hazing of the 
atmosphere intense. But on the 28th a depression was passing to the N. of our 
islands, and the isobars were closing in and becoming regular, with their direction E. 
and W. Winds were, therefore, beginning to set in from the W., and, as will be seen 
from the tables, the pure westerly winds beginning to make themselves felt, the 
number of particles fell from near 10,000 to 1750. On the 1st of March the iso- 
bars closed still further, and were situated more due E. and W. The conditions con- 
tinued to strengthen next day, the 2nd, by which time the isobars had become very close, 
and the winds had veered a slight amount to N. The result of the change is seen in 
the table ; the dust went down to 51 per c.c, or about ■ 2 -^ Ty of what it was three days 
before. During the 3rd, 4th, and 5th, the isobars kept much the same position as on the 
2nd, and the amount of dust continued very low. It may be stated that the isobars 
opened a little on the 3rd and 4th, but came close again on the 5th ; and it will be 
noticed that the dust increased a little on the 3rd and 4th, but decreased again on the 
5th. The interpretation of this may be, that closely-situated isobars indicate great 
general circulation and consequent reduction of local impurity, though it may be noticed 
that the local wind was not so high on the 5th as on the two previous days. 

Dust and Isobars. 

In Part I. it is shown that the amount of dust depends greatly on the force of the 
wind, and also on its direction. In working out the results of these last observations the 
effect of the direction comes out in a very marked way. Although all increase in wind is 
accompanied by a decrease in dust, yet it would appear that certain directions of wind 
have a much greater purifying influence than others, i.e., winds from certain directions 
are purer than those from others. The directions of the purest winds are not the same at 
all stations ; the conditions of the areas surrounding the stations determining the purest 
directions. In Switzerland, the southerly winds are pure, while northerly ones are 



40 MK JOHN AITKEN ON THE NUMBER OF DUST PARTICLES IN THE 

impure. In Scotland, the southerly winds seem to be the most impure, while the 
north-westerly ones are the purest. It would appear that dusty impurities can be carried 
great distances, as they are found in air that has travelled over wide tracts of country 
in which no pollution has been added. 

In studying the distribution of pressure for the periods of these observations in Scot- 
land, it became evident that there was a certain relation between the isobars and the dust. 
In all the cases wherever the isobars were situated east and west, the air was pure, and 
the closer the isobars were the purer it was, which means that under these conditions 
we have westerly winds, and as it comes from the Atlantic, the air is purer than any 
other in our area. Further, if the isobars were situated north and south, even though 
they were fairly close, the wind never brought very pure air, which means that under 
these conditions we have southerly winds, and coming from the polluted districts of 
our country and the Continent it brings much dust with it. It should be remarked that 
during all the tests the relative position of the areas of high and low pressure was 
such as to give us W. winds with east and west isobars, and S. winds when situated 
north and south. 

Air seems to carry its impurities long distances. For instance, southerly winds at 
Alford brought a good deal of dust though they had to travel over a considerable extent 
of mountainous and uninhabited country before coming to the place of observation. As 
bearing on this point, it may be remembered that the discussion of the Kingairloch obser- 
vations showed, that when a cyclone had advanced over our area from the west, and had 
given rise to a circulation of air from France over Holland and northwards over the North 
Sea, that after the centre of the cyclone had passed, and we got northerly winds, the air 
was not always under these circumstances pure ; though northerly winds under most con- 
ditions are pure. It looks as if, under the conditions above described, the air from the 
Continent had circled northwards, and passed over the sea to the north of the station, 
where its curving movement has brought it as a northerly wind to the point of 
observation. 

From these remarks it would appear that we may be able to get an idea of the 
amount of dust in the air by studying the isobars at and before the date. When 
the isobars are close, and situated in an easterly and westerly direction with the 
area of high pressure to the south of the depression, the air will be pure. But if the 
isobars are situated north and south, with the area of high pressure to the right, the air 
will not be so pure. Again, if the isobars are wide the winds will be light, and the air 
tending to become impure ; or, if the isobars are irregular, the circulation will be confusec], 
and the impurity may be very great at times. Further, though N. winds in Scotland 
are generally pure, as they blow from uncontaminated areas, yet it seems probable that 
if they follow a period during which the air of the Continent has been circling northwards, 
they may be sometimes impure. 



ATMOSPHERE OF GREAT BRITAIN AND ON THE CONTINENT. 41 

Dust and Temperature. 

In Part I. diagrams are given showing the maximum and minimum temperatures and 
the amount of dust in the air at the dates of three sets of observations. An examination 
of these diagrams seemed to show that the dust has an influence on the maximum and 
minimum temperatures, as the highest maximum temperatures were observed on the days 
when the amount of dust was greatest. The dust also seemed to have an influence in 
checking the fall of the temperature at night, i.e., high dust was generally accompanied by 
high mean temperature. We, therefore, naturally turn to the observations of 1890 to 
see if they also support this conclusion. The observations made on the Continent being 
too fragmentary, it is unnecessary to consider them. Passing over these, and coming to 
the set of observations corresponding to those shown in the diagrams given in Part I., we 
come first to the Kingairloch observations. As already stated, the weather during the 
period of these observations was much disturbed by frequent cyclones. The skies were 
generally cloudy, and consequently solar and terrestrial radiation would have but little 
influence on the temperature of the air. The Kingairloch observations of 1890 are 
therefore of little use for our purpose, as the maximum and minimum temperatures would 
be determined principally by the winds. It may, however, be stated that during the 
period of the observations the mean temperature of all the weeks was below the average, 
sometimes as much as 5° and 6°, and that during the whole of this period the amount of 
dust was much lower than in 1889, and was probably much below the mean, as excep- 
tionally low readings were frequently obtained during this period. 

On examining the Alford observations the result is similar to that pointed out in the 
diagram for 1889. Mr Buchan having again kindly supplied me with a copy of the 
Logie Coldstone temperature observations for 1890. (It may be mentioned that Logie 
Coldstone is one of the Scottish Meteorological Stations, and is situated in a south- 
westerly direction at a distance of about 10 miles from Alford.) From these observations 
I find that the highest maxima were recorded on the 8th, 1 3th, and 1 4th ; on these 
days the temperature went up to 72° or more. From the table for 1890 it will be 
seen that on these days the dust was also about its maximum. Again, the lowest 
minimum was recorded on the 10th, at which date the dust was also at a minimum. It 
would, however, be rash to draw a conclusion on so important a point from so few observa- 
tions as are yet at our disposal. As has been already stated, we must have more observa- 
tions, and the observations of radiation, both solar and terrestrial, must be continuous 
before we can get any satisfactory answer to this question. 

As an illustration of the influences at work affecting the temperature of the air, I find 
that if we add to the diagram showing the dust, and the temperature, another curve to show 
the number of hours of sunshine, we shall find this latter curve and the curve of maximum 
temperature to be very similar, and therefore, the high maxima may be due to long 
hours of sunshine. Since the curve of maximum temperatures follows the curve of hours 
of sunshine, the dust curve must also follow the curve of sunshine, all three rising and 

VOL. XXXVII. PART I. (NO. 3). H 



42 MR JOHN AITKEN ON THE NUMBER OF DUST PARTICLES IN THE 

falling together. And one now naturally asks, What can be the relation between the 
amount of dust and the number of hours of sunshine ? So far as the observations go at 
present the reason for the close relation observed at this station is, that the same winds 
— viz., southerly ones — that brought the high dust also brought clear skies, and when 
the wind went either E. or W., though it brought a purer air, it also brought cloudy skies, 
and the lower temperature may in part have been due to the clouds. 

Turning now to the observations made in the end of February and beginning of 
March of 1891, let us see what information they give on the effect of the dust on the 
temperature. As will be seen from the table, the amount of dust in the air in the end of 
February was excessive, and from other observations, which are not entered in the table, 
I find that during most of the month the air was very full of dust. On turning 
now to the Meteorological Report for February it will be found that the average weekly 
temperature for the stations in Scotland was above the mean, and was frequently very 
high for that month. The warm weather of February was certainly accompanied by a 
very dusty atmosphere ; the dust, however, may or may not have been the cause of the 
high temperature. Turning again to the table, we see that the amount of dust suddenly 
fell in the beginning of March to an exceptionally low figure, and that it continued low 
for some days. On now consulting the Meteorological Eeport for March, we find that 
the mean temperature for these days was not low, but over our area it was 2° above 
the average. Here the relation between the dust and the temperature seems to break 
down, as the air was very pure, and yet the mean temperature was high. Let us, 
however, examine the conditions more closely, and I think it will be admitted that the 
facts are open to quite a different interpretation. It is true the mean temperature was 
above the average on the days when the dust was very low. But during all these days 
the wind blew with great force and the skies were clouded, so that the temperature of 
the air would be entirely governed by what the winds brought us. As it was winter, it 
was probable that the winds would bring a temperature higher than the mean, just as in 
summer they will probably bring a lower. If we are to find any effect from the low 
dust observed during the first days of March, we must look for it in the conduct of the 
air after the wind has fallen. The weather charts for March, from the 1st to the 
6th, both included, all show the isobars to be close, regular, and across the map. On 
the 7th the isobars began to widen out, and from the 8th on to the 15th they were wide 
and irregular, indicating light and variable winds ; and during these eight days there was 
no steady inflow of air from any impure direction, so that the pure air which covered our 
area in the beginning of the month probably circulated backwards and forwards over our 
area. Though the lower air would be becoming impure, yet as the winds were light, and 
being the winter season, the impurity would not ascend to the upper air, so that 
probably the upper air remained pure. The Meteorological Report shows that during 
the second week of March, after the winds had fallen, the temperature became exces- 
sively low, the different stations in Scotland for that week being as much as from 
8° to 11° below the mean. 



ATMOSPHERE OF GREAT BRITAIN AND ON THE CONTINENT. 



43 



It may, of course, be contended that we are here stretching a point to support the 
theory that dust checks terrestrial radiation and consequent cooling, as the only 
evidence produced to show that the air was pure during the cold period is the direction 
of the air circulation after the country was covered with pure air. However, as the 
circulation was purely local, it seems probable the increase in impurity would be slow 
compared with the sudden increase of dust which we have seen takes place with a change 
of circulation. 

After writing the above, it appeared to me that the point was one of some importance, 
and worth following up. I therefore trespassed so far on the kindness of the Scottish 
Meteorological Society as to ask for information regarding the state of the air as observed 
on Ben Nevis during March. Mr Rankin, the observer at that date, has kindly written me 
as follows : — " The observations of March dust are very interesting. There are two well- 
marked periods of purity, 1st to 12th, beginning and ending sharply, again 25th to 29th." 
During the first period the numbers were excessively low ; a not unusual reading was 7 
per c.c, and sometimes it was much lower. From the extract from Mr Rankin's letter it 
will be seen there was the same rapid change on the Ben from impure to pure air in the 
beginning of March as was observed at low level. It will be also seen that during the 
period of excessively low temperature at low level, the upper air was remarkably free from 
dust. In this case the evidence in support of the relation between the dust and tempera- 
ture is very strong, as the air was exceptionally cold during this exceptionally pure 
period. 

Table of the Number of Dust Particles in the Atmosphere. 



Place. 


Date. 


Hoxir. 


Number of 

Particles 

per c.c. 


Wind. 


Tempera- 
ture. 


Humidity. 


State of 
the Air. 


Remarks. 




1890. 
















H yep.es . . 


Mar. 31 
April 


3.30 p.m. 


725 


S.W. 3 


56 


9-5 


Very clear 


Observed on Fenouillet. 


)> 


1 


3 P.M. 


15,250 


E. 2 


59- 


5 


Very thick 


» » 


Cannes . . 


5 


5 P.M. 


2,850 


N. 0:2 


58 


6 


Haze 


Observed on La Croix des 
Gardes. 


>) 


7 


10.45 a.m. 


1,275 


N. 0'2 


60 


8 


Medium 


» » 


Mentone . . 


11 


4 P.M. 


14,000 


W. 3 


56 


)> 


Thick haze 


Observed on hill 800 feet 
high. 


)> 


12 


4.30 p.m. 


875 


N. 1 


48 


3-5 


Clear 


Observed on hill. Snow on 
hills to half-way down. 


i) 


14 


3 P.M. 


810 


S.E. ? 1 


50 


4 


Raining 


Raining all the 13th, 


!> 


16 


3 P.M. 


900 


E. ? 0'5 


54-5 


2-5 


Medium 


Observed on hill. 


)> 


19 


4 P.M. 


26,000 


S.E. 0'5 


58 


3-5 


Thick 


Observed on hill. Number 
varied greatly. 


Bellagio . . 


23 


3 P.M. 


6,300 


S. 2 


65 


8 


Thickish 
haze 


Limit of visibility 15 miles S. 


>» 


24 


10 A.M. 


1,225 


N. 4 


58-5 


16 


Clear 








11.30 A.M. 


5,300 


N. 1 


59 


16 


Hazy 


Air much thicker than at 

10 A.M. 



44 



MR JOHN AITKEN ON THE NUMBER OF DUST PARTICLES IN THE 



Table of the Number of Dust Particles in the Atmosphere — continued. 



Place. 


Date. 


Hour. 


mber of 
irticles 
er c.c. 


Wind. 


ft £ 

2 5 


3 


State of 
the Air. 


Remarks. 












H 












April 
















Bellagio . . 


25 


11 A.M. 


7,600 


S. 0-2 


53 


5 


Thick 


Limit of visibility 1 5 miles N. 






4.30 p.m. 


4,100 


)> 


52 


3 


Very thick 


Air thicker than in morning. 


>) 


26 


12 A.M. 


1,150 


N. 5 


48 


4 


Clear 








5.15 p.m. 


900 


)» 


47 


6 


Very clear 


Air getting clearer. 


>) 


28 


11 A.M. 


10,250 


? 


55 


7-5 


Clear 


Too high from local impuri- 
ties,due to absence of wind. 


!) 


29 


10 A.M. 


900 


N. 3 


60 


15 


Very clear 


Ahnost no haze through 15 
miles N., and only a little 
through 15 miles S. 






11 A.M, 


600 


N. 2 


61 


15-5 


Extremely 
clear 




)) 


30 


10 A.M. 


20,500 


S. 0-2 


55 


7 


Thick haze 


Too high from local pollution. 

Limit of visibility 1 5 miles 

S. 
Taken in boat on Lake. Be- 






11 A.M. 


5,200 


i) 


52 


4 


Thick 




May 














ginning to rain. 


Baveno . . 


3 


10 A.M. 


7,700 


E. 0-2 


64 


9 


Thickish 
haze 








11 A.M. 


10,750 


>j 


54 


4 


)) 


Taken in boat on Lake. 






3 P.M. 


1,750 


E. 2 


61 


9 


Medium 


Taken on land. 


Simplon Pass 


5 


4.30 p.m. 


6,000 


S.E. 0-5 


54 


1 




Rain just ceasing. 


Baveno . . 




6 P.M. 


7,800 


S.E. 0-2 


54-5 


5-5 




Taken at Baveno. 


>) 


6 


10.30 A.M. 
12 A.M. 


16,000 
14,125 


S.E. 0-1 


62 


10 




Probably local impurities. 
Taken in boat on Lake. 






3 P.M. 


4,200 


S.E. 2 


62 


10 




Increase of wind, reduction 
of dust. 


Simplon Pass 


7 


4 P.M. 


2,010 


W. 3 


52 


2 


Thick 




Baveno . . 


9 


11 A.M. 


5,400 


N.E. 0-2 


63 


7 


Hazy 


Wind inshore. 






11.30 A.M. 


5,100 


)5 


60 


>? 


)> 


Taken in boat on Lake. 






12 A.M. 


4,100 


S.E. 0^3 


61 


5) 


)> 


Taken on shore. 






12.30 p.m. 


2,600 


S.E. 1 


)? 


II 


>» 


Wind increasing. 


Locarno . . 


13 


5 P.M. 


4,500 


1 


56 


2? 


Thickish 


Raining, wind slight and 
variable. 


Lucerne . . 


14 


6 P.M. 


4,000 


1 


53 


2 1 


Thick 


Been raining, wind slight. 


VlTZNAU . 


15 


2.45 p.m. 


11,080 


S. 0-2 


64 


10 


Thick haze 


Hills thickly veiled in haze. 


RlGI KULM . 


I 5 


4.45 p.m. 


3,400 


N.E. 0-2 


44 


2 


Thickish 


Air extremely thick looking 
downwards, and thickish 
at level. 






5.30 p.m. 


4,100 


E. 0-2 


41 


2 


)) 








6 P.M. 


4,200 


N. 0'2 


>) 


j) 


»> 




)) 


16 


9 A.M. 


1,500 


S.E. 0-5 


52 


5 


Hazy 








9.30 a.m. 


1,150 


)? 


)J 


6 


?! 








10.30 A.M. 


1,325 


» 


55 


8 


>) 








3.30 p.m. 


6,600 


)5 


50-5 


4 


Thick haze 


Increase in dust, probably due 
to lower air rising. 






5.30 p.m. 


6,700 


J) 


49 


4-5 


)> 




>> 


17 


9 A.M. 


2,100 

1,950 
1,200 


E. 0-5 


52 


6 


Thickish 
haze 

!) 
)) 


Wind variable, changing from 
S. of E. to N. of E. 



ATMOSPHERE OF GREAT BRITAIN AND ON THE CONTINENT. 



45 



Table of the Number of Dust Particles in the Atmosphere — continued. 









O W 

7 © r* 




h 


£ 






Place. 


Date. 


Hour. 


f-4 I 1 ^ 

sis 


Wind. 


CD CD 
CD 

H 




State of 
the Air. 


Remarks. 




May 
















Rigi Kulm . 


17 


10 A.M. 


1,450 


E. 0-5 


56 


8 


Thickish 
haze 


- 






12.15 p.m. 


6,100 




52 


4 


Thick haze 








5.30 p.m. 


4,500 


N.W. 1 


)> 


5 


» 


Air much the same as on two 
previous evenings. 






5.45 p.m. 


4,500 




>> 


n 


»j 




)> 


18 


7.45 a.m. 


1,700 


S.E. 1 


48 


4-5 


Thickish 
haze 


Clouds passing over hill. 






10 A.M. 


1,450 
1,350 


S. 1 

J) 


51 

50 


5 
6 


13 


Clouds forming below top of 
hill, top clear. 






12.15 p.m. 


3,800 


)) 


55 


)> 


J) 


Halo at 10 a.m. 






12.20 p.m. 


3,800 


JJ 


56-5 


7-5 


J) 








6.10 p.m. 


3,000 


N. 2 




... 


Extremely 
thick 


Raining ; thunderstorm since 

5 P.M. 






6.20 p.m. 


810 


JJ 




... 


» 


Violent storm of thunder, 
lightning, and hail. 






7.10 p.m. 


725 


. . • 






JS 








7.15 p.m. 


725 


... 




. .. 


!) 




)» 


19 


9 A.M. 


700 


S. 2 


48-5 


5-5 


Medium 


Much clearer than any 
previous morning. 






9.15 A.M. 


700 


J) 


!) 


J) 


53 








12.15 p.m. 


775 


S.W. 3 


54 


9-5 


Fairly clear 


Clearer than in morning. 








550 


JJ 


>) 


>) 


j) 








12.30 a.m. 


650 


J) 


)> 


)> 


)> 








2 P.M. 


450 


JJ 


53 


10 


Clear 








2.15 p.m. 


420 


JJ 


!' 


)) 


» 








5.30 p.m. 


420 


JJ 


50 


8 


Very clear 


In the afternoon the Jura 
Mountains and Zurich were 
visible for first time ; Hoch- 
gerrach was also distinctly 
visible. 








375 


JJ 


>) 


)i 


») 








5.40 p.m. 


425 


JJ 


)> 


)> 


jj 




)> 


20 


9 a.m. 


1,200 


S.E. 1 


50 


4 


Medium 








9.10 A.M. 


1,250 


>) 


51 


5 


?5 








12.10 p.m. 


9,500 


E. 1 


54 


6 


Thick haze 


Air like what it was at 
beginning of visit. 






12.20 p.m. 


12,000 


E. 1 


52 


7 


jj 




VlTZNAU . 


20 


3 p.m. 


10,250 
6,000 

3,500 


W. 0-2 

S.E. 1 


71 


11 


jj 
j' . 


Wind slight and inshore. 
Wind increasing and coming 
offshore. 








2,900 


S.E. 2 


74 


17 


jj 










2,550 


• . ■ 


74 


16 


jj 










1,750 




74-5 


18-5 


»> 








3.45 p.m. 


1,700 




74 


18 


"... 








4 P.M. 


12,250 


W. 1 


68 


10 


j j. 


Wind inshore. 






4.10 p.m. 


13,000 


W. 2 


!) 


>) 


jj 




PlLATUS KULM 


22 


12.20 p.m. 


1,050 


1 


40-5 


0-5 


Fog 


! 



46 



MR JOHN AITKEN ON THE NUMBER OF DUST PARTICLES IN THE 



Table of the Number of Dust Particles in the Atmosphere — continued. 









O 03 




ci 


>> 

+3 






Place. 


Date. 


Hour. 


mbei 
uticl 
er c.( 


Wind. 




72 


State of 
the Air. 


Remarks. 








-i 2-1 




H 


w 








May 
















PlLATUS KULM 


22 


1 P.M. 


875 


1 


48 


2 


Fog 








1.30 p.m. 


625 


. . . 


47 


1 


n 








2.30 p.m. 


1,275 




43 





j> 


Fog very dense. 






4.30 p.m. 


800 


S.W. 0'2 


43 


0-5 


» 


Raining. 




July 
















KlNGAlRLOCH . 


1 


5 P.M. 


2,000 


E. 0-5 


62 


10 


Hazy 


20 m. |. 


>> 


2 


10 A.M. 


2,325 


E. l' 


59 


5 


Thickish 


20 m. tV 






6 P.M. 


875 


N. 1 


56 


4 


Medium 


20 m, |. 






6.15 p.m. 


825 


)> 










)! 


3 


10 A.M. 


483 


N.W. 0-2 


60 


4? 


Clear 


20 m. ^q, showers. 








500 


» 


>) 


J) 


n 


Humidity too high local. 






6 P.M. 


3,050 


N.W. 2 


56 


6 


>j 


20 m. / , 


)> 


4 


10 A.M. 


265 


)> 


60 


8 


Very clear 


Sky blue to the horizon. 






11.30 P.M. 


484 


>> 


60-5 


8-5 


it 








4 P.M. 


1,625 


N.W. 3 


62 


9 


>) 








6 P.M. 


2,550 


N.W. 2 


56 


7 


Haze 




)! 


5 


10 A.M. 


300 


)) 


59 


JJ 


Very clear 








11.30 a.m. 


465 


)) 


60 


>) 


Clear 








1 P.M. 


410 


N.W. 3 


>j 


8 


j> 


Passing showers. 






6 P.M. 


250 


N.W. 2 


54 


5 


)> 


20 m. \ ; mist on hills. 


5) 


6 


10 A.M. 


450 


N.W. 3 


60 


7 


>> 








7 P.M. 


3,750 


N.W. 2 


52-5 


4-5 


Medium 


20 m. \. 


>> 


7 


10 A.M. 


280 


W. 0-2 


53 


2 


Thick 


Limit 12 m. 






1 P.M. 


236 


» 


52 


» 


JS 


Limit 6 m. 






1.30 P.M. 


176 


j> 


)> 


>> 


)> 


Raining. 






6 P.M. 


3,350? 


>) 


50 


>) 


Very thick 




I) 


8 


10 A.M. 


1,100 


N.W. 2 


57 


6? 


Very clear 


20 m. j^ ; been rain. 






12.30 p.m. 


1,650 


>j 


58 


8 


>> 


>) 






4 P.M. 


1,200 


N.W. 1 


55 


6 


Very clear 


20 m. y^ ; showers. 






9 P.M. 


750 


!) 


48 


3 


Thickish 


1 2 m. y 1 ^ ; been rain. 


)> 


9 


10 A.M. 


985 


N.W. 3 


52 


4 


j) 


12 m. |; showery. 






1 P.M, 


810 


N.W. 2 


58 


5'5 


i) 


12 m. |; showery. 






6 P.M. 


975 


j) 


54-5 


2-5? 


Clear 


20 m. | ; showery. 


)> 


10 


10 A.M. 
2 P.M. 


625 
1,000 


ii 


55 


7 


Thin haze 








7 P.M. 


650 


N.W. 1 


48 


4 


Hazed 


20 m. ^. 


)> 


11 


10 A.M. 


3,100 


Calm 


53 


7 


Clear 








12.15 p.m. 


4,800 


Calm 


56 


8 


» 








1 P.M. 


5,300 


N. 1 


. . . 




>) 


Number varying a good deal. 






1.30 P.M. 


3,400 


)> 


57 


9 


)> 








3 P.M. 


2,300 


N.W. 2 


> . • 


. . . 


19 








6 P.M. 


3,570 


» 


52 


6 


J) 


20 in. t2 . 


)) 


12 


10 A.M. 


4,200 


S. 1 


54 


4 


Thick 


12 m. J. 






11 A.M. 


800 


>) 


ii 


4-5 


ii 


12 m. | ; slight rain. 






3 P.M. 


975 


S.W. 1 


51 


2? 


i) 


12 m. |; been a shower. 






6 P.M. 


485 


S. 0-5 


>» 


i> 


Very thick 


Limit 15m.; raining. 


1) 


13 


10 A.M. 


82 


S.W. 0-5 


59-5 


1-5 


j) 


Limit 6 m. ; raining. 






10.30 A.M. 


61 


)» 


>) 


>> 


u 


!> 






2 P.M. 


45 


>> 


)> 


jj 


>) 








2.10 p.m. 


77 






... 


!) 





ATMOSPHEEE OF GREAT BRITAIN AND ON THE CONTINENT. 



47 



Table of the Number of Dust Particles in the Atmosphere — continued. 



Place. 


Date. 


Hour. 


Number of 

Particles 

per c.c. 


Wind. 


k 

S B 

CB 

H 


1 


State of 
the Air. 


Remarks. 




July 
















KlNGAIRLOCH . 


13 


2.20 p.m. 


137 


SW. 0-5 


59'5 


1-5 


Very thick 








6 P.M. 


16 


W. 


59 


)) 


>> 


Heavy rain. 






6.10 p.m. 


26 


)) 


» 


JJ 


>j 


jj 






6.20 p.m. 


38 


J> 


)) 


)J 


j) 


u 






6.30 p.m. 


33 


3) 


j) 


J) 


>> 


jj 






6.40 p.m. 


29 


)) 


J5 


JJ 


>) 


jj 


JJ 


14 


10 A.M. 


550 


W. 1 


54 


3 


Thickish 


6 m. j^ ; showers. 






1 p.m. 


550 


W. 2 


55-5 


3-5 


Thick 


Raining. 






6 P.M. 


700 


W. 1 


57 


4 


Thickish 


12 m. |; showers. 


» 


15 


10 A.M. 


475 


)) 


56 


JJ 


Clear 


Showers. 






1.20 p.m. 


1,800 


») 


58 


4-5 


Thickish 


1 2 m. \ ; showers. 






2.20 p.m. 


700 


W. 2 


62 


6-5 


Clear 


12 m. jV 






6 P.M. 


2,800 


N.W. 1 


57-5 


4 


» 




n 


16 


10 A.M. 


6,400 


S.W. 0-5 


58-5 


4-5 


Hazy 


12 m. 1 






10.45 a.m. 


1,500 


W. 0-5 


60 


6 


Medium 


20 m. £. 






1 P.M. 


2,650 


S. 0-2 


56 


3-51 


>> 


20 m. j ; showers. 






2.30 p.m. 


3,500 


S.W. 1 


60 


8 


j) 








6 p.m. 


825 


N.W. 1 


55-5 


75 


Very clear 




>> 


17 


10 A.M. 


6,100? 


S.E. 1 


59 


7 


Haze 


Steamer 5 miles to windward. 






10.15 A.M. 


2,900 


)) 


57-5 


7-5 


» 








1 P.M. 


1,450 


N.W. 0-2 


59 


8 


Clear 








2 P.M. 


2,100 


N.W. 2 


58 


j) 


>> 








6 P.M. 


700 


N.W. 0-5 


54 


6 


Very clear 


20 m. T V 


5! 


18 


10 A.M. 


560 


I 


53 


2 


Very thick 


Limit 6 m. ; raining. 






1 P.M. 


560 


Calm 


54-5 


2-5 


)i 


Limit 6 m. ; misty rain. 






6 P.M. 


1,000 


>) 


55 


2 


)5 


Limit 6 m. ; misty rain. 


V 


19 


10 A.M. 


1,400 


N.E. 1 


60 


6 


Hazy 


20 m. |. 






2.15 p.m. 


4,800 


E. 1 


63 


9 


Very clear 


Bluish haze. 






3 P.M. 


7,600 


>5 


64-5 


8-5 


)> 


ji 






6 P.M. 


4,100 


N.W. 2 


59-5 


7 


jj 


j? 






8.15 p.m. 


1,420 


i) 


55 


5J 


>) 




)) 


20 


10 A.M. 


535 


Calm 


56 


35 


Thick 


Raining ; carry W. 






3 P.M. 


550 


N.W. 0-5 


60 


5 


Clear 


20 m. Jjj. 






7 P.M. 


735 


E. 0-2 


55 


1 


Very thick 


Raining. 


1! 


21 


10 A.M. 


66 


N.W. 2 


62 


4 


Clear 


6 m. ^V > distance clouded. 






10.45 a.m. 


42 


)> 


)> 


?) 


jj 








12.30 p.m. 


58 


Calm 


66 


)> 


j> 


10 m. y^ ; distance clouded. 


. 




1 P.M. 


53 


S.E. 0-2 


64 


)> 


jj 


j> 






3 P.M. 


150 


N.W. 1 


60 


3 


Very thick 


Misty rain. 






6 P.M. 


44 


>) 


58 


2 


j> 


6m,|; misty rain. 


1) 


22 


10 A.M. 


610 


N.W. 3 


58 


6 


Hazy 


10 m. \ ; cloudy. 






1 P.M. 


600 


N.W. 4 


57-5 


4-5 


Thickish 


10 m. \; slight rain. 






3 P.M. 


635 


N.W. 3 


58-5 


>) 


jj 


» 






6 P.M. 


500 


>] 


57 


5 


j> 


Blowing hard all day. 


)> 


23 


10 A.M. 
10.30 A.M. 

11 A.M. 
11.20 A.M. 
11.40 A.M. 

12 A.M. 


48 
37 
28 
28 
23 
19 


n 


58 


1 


Very thick 
u 
jj 
jj 
jj 
>j 


\\ m. \ ; drifting rain. 



48 



MR JOHN AITKEN ON THE NUMBER OF DUST PARTICLES IN THE 



Table of the Number of Dust Particles in the Atmosphere — continued. 



Place. 


Date. 


Hour. 


Number of 

Particles 

per cc. 


Wind. 


u 

8 p 

2 5 

CD 

H 


>> 

a 
3 

w 


State of 
the Air. 


Remarks. 




July 
















KlNGAIRLOCH . 


23 


1 P.M. 


148 


N.W. 4 


59 


2 


Very thick 


Sky clearing. 






3 P.M. 


258 


N.W. 3 


58 


3 


Medium 


6 m. -jJfy ; rain ceasing. 






6 P.M. 


237 


N.W. 2 


55-5 


4 


Thickish 


10m.|; been blowing very 
hard. 


>> 


24 


10 A.M. 


151 


N.W. 2 


57 


5-5 


ii 


10 m. J ; showers. 






1 P.M. 


210 


N.W. 3 


58 


6 


Clear 


10 m. sV 






6 P.M. 


200 


N.W. 1 


52-5 


1-5 


Thick 


Raining. 


o 


25 


9 A.M. 


253 


i) 


56 


4 


Very clear 


10 m. ^ , 






10 A.M. 


203 


N.W. 0-5 


ii 


ii 


Clear 


10 m. jJq ; a few drops of rain. 






3 P.M. 


1,325 


S. 0-5 


59-5 


5-5 


Hazy 


10 m. \. 






6 P.M. 


2,200 


S.E. 0-5 


57 


6 


Clear 


20 m. tV 


j) 


26 


9 A.M. 


1,450 


ii 


57 


1 


Extremely 
thick • 


Limit l| m.; raining. 






10 A.M. 


1,950 


ii 


58 


1-5 


ii 


Raining. 






1 P.M. 


37 


W. 0-5 


63 


3 


Thick 


Misty rain. 






3 P.M. 


55 


W. 1 


64 


1-5 


ii 


ii 






6 P.M. 


290 


W. 0-5 


56 


3 


Clear 


10 m. tV 


)> 


27 


10 A.M. 


800 


S. 1 


56 


2 


Very thick 


\\ m. \; raining. 






3 P.M. 


1,437 


S.W. 1 


62 


7-5 


Thin haze 








7 P.M. 


1,950 


S.E. 2 


57 


5 


Thickish 


10 m. 1 


)> 


28 


10 A.M. 


1,050 


S.W. 1 


54 


4 


Clear 


Passing showers. 






1 P.M. 


825 


W. 3 


60 


5 


Thick 


n ii 






3 P.M. 


860 


ii 


55 


3 


ii 


ii ii 






7 P.M. 


1,035 


N.W. 3 


56 


4 


ii 


Passing showers ; very stormy 
on loch. 




Sept. 
















Alfoiw . . 


8 


6 P.M. 


3,400 


W. 0-5 


62 


7-5 


ii 


Thick haze ; fine day. 


11 


9 


10 A.M. 


750 


ii 


56 


3 


Medium 


Cloudy. 






11 A.M. 


325 


N.W. 1 


60 


5 


Clear 


Half clouded. 






5.30 P.M. 


3,700? 


S.E. 0-2 


54 


2-5 


Thick 


Beginning to rain. 


)> 


10 


10 A.M. 


127 


N.W. 1 


55-5 


7 


Very clear 


Cloudy. 






5 P.M. 


192 


W. 


56 


5-5 


ii 


Clouded all day. 


II 


11 


10 A.M. 


242 


N.W.N. 3 


54-5 


4 


ii 


Showers on hills. 






5 P.M. 


1,825 


n 


54-5 


4-5 


Clear 


Numbers variable. 


II 


12 


10 A.M. 


192 


N.W.N.1 


60 


6 


Very clear 


Clouded. 


II 


13 


10 A.M. 


2,000 


E. 0-2 


63 


7 


Hazy 


Numbers very variable. 






5.30 P.M. 


4,400 


S.W. 1 


61 


5 


Thick haze 


Wind been S. 


, 11 


15 


10 A.M. 


3,900 


S.S.E.1-5 


53-5 


2 


Extremely 
thick 


Clouding over. 






1.30 p.m. 


4,000 


S. 1 


58 


4 


n 


Clouded. 






5.30 p.m. 


3,300 


ii 


56 


2 


ii 


ii 


II 


16 


10 A.M. 


4,300 


S. 1-5 


57-5 


3 


ii 


Passing clouds. 






5.30 p.m. 


3,900 


S. 1 


56-5 


2-5 


ii 


Cloudy. 


II 


17 


10 A.M. 


2,350 


S. 2 


55-5 


1-5 


ii 


Thickest day here. 






5.30 p.m. 


1,850 


ii 


55-5 


3 2 


Very thick 




>l 


18 


10 A.M. 


4,750 


S. 1 


58 


2 


Extremely 
thick 


Dull, clouded. 






6 P.M. 


6,800 


ii 


57-5 


2-5 


ii 


Quarter clouded. 


II 


19 


10 A.M. 


1,950 


S. 0-2 


56 


2 


n 


Raining during night. 



ATMOSPHERE OF GREAT BRITAIN AND ON THE CONTINENT. 



49 



Table of the Number of Dust Particles in the Atmosphere — continued. 













<k 


£ 






Place. 


Date. 


Hour. 


Number 
Particl 
per c.c 


Wind. 


Tempei 
ture. 




State of 
the Air. 


Remarks. 




Sept. 
















Alford . . 


19 


6 P.M. 


1,850 


S. 0-5 


54 5 


2 


Extremely 
thick 


Dull, clouded. 


j> 


20 


10 A.M. 


1,025 


S.S.E.1-5 


56 


2 


Thickish 


Clearing. 






6 P.M. 


2,300 


S. 1 


54 


2 5 


Thick 


Been raining. 


it 


22 


10 A.M. 


2,850 


S. 0-2 


52 


2 


)) 


Fine morning ; half clouded. 


Callievar . . 


5) 


12.30 p.m. 


710 


S.W. 3 


57 


5 


Thickish 


Cairngorms just visible. 






2 P.M. 


1,200 


S.W. 2 






Thick 


Air thicker. 






2.10 p.m. 


1,385 


5) 


58 


4-5 










2.30 p.m. 


1,575 


» 


56 


4 










3 P.M. 


1,050 


)) 


55 


4 


Thickish 


Air clearer. 


Alford . . 


55 


5 P.M. 


2,700 


Calm 


575 


35 


Thick 


Quarter clouded. 






5.30 p.m. 


2,100 




57 


4 


j? 


55 55 


)i 


23 


10 A.M. 


4,200 


S. 0-2 


55-5 


2-5 


Extremely 
thick 








6 P.M. 


3,000 


N.E. 0-2 


55 


2 


>; 


Raining. 




1891 
















Oarelochhead 


Feb. 27 


12.30 p.m. 


7,250 


Calm 


40 


3 


>> 


Limit of visibility 2 miles low 
down ; 4 high up. 






1 P.M. 


7,500 


55 


n 


JJ 


55 


55 55 


Whistlefield 


>> 


4 P.M. 


9,000 


E. 0'2 


43 


3 5 


)) 


Limit of visibility 3 low 
down ; 4 high up. 








9,750 


ji 


42-5 


3-5 


)) 




Garelochhead 


28 
March 


12.30 p.m. 


1,750 


S.W. 2 


44-5 


4-5 


Thickish 


Dull. 


55 


2 


4 P.M. 


82-5 
68 
83 
51 


N.W. 2 

)) 
J) 

J) 


40-5 


3 5 


Very clear 


Clouded ; beginning to rain. 






6 P.M. 


62 


)J 


40 


4 


?) 




)) 


3 


11 A.M. 


143 


N.W. 4 


36 


2 


Clear 


Passing showers, hail and rain. 






5 P.M. 


154 


N.W. 5 


40 


2-5 


)) 


55 55 


55 


4 


12 A.M, 


175 


N.W. 5 


48 


1 


Thickisli 


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4 P.M. 


192 


;> 


48-5 


15 


55 


55 


55 


5 


12 P.M. 


715 


N.W. 1 


54 


1 


55 


55 



VOL. XXXVII. PART I. (NO. 3). 













AT 


BEN 


NEVIS AND 


KINGAIRLOOH 


Trans. 


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DIAGRAM SHOWING THE NUMBER OE DUST PARTICLES IN THE ATMOSPHERE AT BEN NEVIS AND KINGAIRLOCH 

DURING JULY 1890. 

































































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The Thin Line Bhows the number of Particles at Ben Nevis. 
The Thick Line shows the number of Particles at Kingairloch. 



The Upper Arrows show the direction and force of the Wind on Ben Nevis. 
The Lower „ „ n _ at T^g^iv^ 

The Intermediate „ „ of the w-inds over the British Isles. 



( 51 ) 



IV. — On the New Star in the Constellation Auriga. By Professor Ralph Copeland, 
Astronomer-Royal for Scotland. Together with Observations of the Same. By 
Dr L. Becker. With a Plate. 

(Read 15th February 1892.) 

The discoverer of Nova Aurigse is the Rev. Thomas D. Anderson of Edinburgh, D.Sc. 
in Classical Philology. Dr Anderson is " almost certain " that he saw the star at 2 a.m. 
on January 24 of this year ; it was then slightly brighter than x Aurigse. Unfortunately, 
he mistook it for 26 Aurigse, which it precedes by about 6 m 39 s , merely remarking to 
himself that the star was brighter than he had previously thought it to be. Twice in the 
following week he made the same observation at about the same hour of the night. At 
last, on the morning of January 31, it flashed upon him that, after all, the star was not 
26 Aurigse, and that 26 Aurigse had a much greater right ascension. He consulted a 
small star-map, and the discovery was made. Regretting that he had not earlier com- 
pared the map with the heavens, and thinking that the star might be well known to 
astronomers, Dr Anderson wrote an anonymous postcard to me on the same morning 
bearing the words : — " Nova in Auriga. In Milky Way, about two degrees south of 
X Aurigse, preceding 26 Aurigse. Fifth magnitude, slightly brighter than x-" I may 
add that Dr Anderson's plant consists of a small hand spyglass adapted to astronomical 
purposes by removing the front pair of lenses from the eyepiece. In this state it 
magnifies about ten times, and, of course, gives inverted images. Dr Anderson hopes 
that amateurs, although provided with only the most modest appliances, may, by his 
unexpected success, be induced to persevere in their observations. 

I have examined a large number of star-maps and catalogues, ancient and modern, 
without finding any previous record of the new star. Several stars are mentioned by 
Sufi as being visible in the tenth century which we cannot now identify, but they seem 
certainly to have no connection with the Nova. Two stars named " the Shaker " and 
"the excellent Milch Camel" may, however, possibly be identified by a study of certain 
Arabian authors referred to by Sufi. 

As to our observations of the Nova at the Royal Observatory, its place has been 
found by differential methods by Mr Heath, First Assistant Astronomer, using the 
transit instrument, and by Mr J. A. Ramsay, student of astronomy, observing with the 
Mural Circle. The mean co-ordinates for 1892*0 derived by them are : — 

R.A. = 5 h 25 m 3*25±0-"02 (9 obs.). DecL = +30° 21' 48-"76±0-"09 (7 obs.). 

Already on the night of February 1, a small spectroscope revealed the presence of 
bright lines, of which some account was at once telegraphed to the Central Station for 
Astronomical Telegrams at Kiel, and also to the President of the British Association, 

VOL. XXXVII. PART I. (NO. 4). K 



52 



PROF. COPELAND AND DR L. BECKER ON THE 



Dr W. Huggins. Already in the daytime, before the star was visible, a message had 
been forwarded to Greenwich Observatory. 

The remarkable nature of the star's spectrum once established, Dr Becker imme- 
diately set about packing the most suitable apparatus to take to Dunecht, where the 
15-inch refractor is fortunately still in perfect adjustment. Meanwhile I arranged to 
keep a record of the star's magnitude, and try what could be done with the apparatus at 
Calton Hill. Owing to the great loss of light in the universal spectroscope of the 24-inch 
reflector, it soon became evident that only a few of the very brightest lines of the 
spectrum could be measured therewith, while it was impossible when using it to obtain a 
good general idea of the spectrum and its possible changes. Eventually I returned to a 
small instrument of Vogel's pattern, which had proved useful on former occasions. * 
With it were obtained, on February 9, a set of measures which eventually yielded the 
following rough approximations to the positions of the principal bright lines in the 
spectrum of the Nova : — 



Wave-length. 


Relative 
Brightness. 


Remarks. 


mmm. 

657-1 

645 

594-2 

5621 

534-5 

519-3 

503-2 

495-25 

487-1 

450-8 


10 

2 
3 
6 
10 
5 
3 
4 
1 


C. 

Edge of black band extending from C. 

Possibly an inaccurate place of D. 

Possibly carbon band or magnesium. 

Bright band near nebular line, but not identical therewith. 

Near nebular line, but also distinct therefrom. 

F. 

Extremely faint ; place very uncertain. 



Eespecting the brightness or "magnitude" of the star there is a telegram from 
Professor Pickering of Harvard College, Cambridge, Mass., dated February 5 : — " Nova 
bright on photograph December tenth, faint December first, maximum December twenty, 
spectrum unique." This is understood to mean that the star could be detected on a 
photograph taken on December 1, that it was brighter on December 10, and brighter 
still on December 20. At least, this is the very probable reading offered by Professor 
Krueger of Kiel. So far as is known, there is no certain record of the star's having 
been seen or photographed previous to December 1, 1891. A faint star seen by Krueger 
near to the spot, 1858, March 23, in one of the revisional zones of Argelander's Atlas, 
has been identified in the heavens near to the Nova. Then we have Dr Anderson's 
observations, January 23 to January 30 — Nova slightly brighter than x Auriga?, 4 "8 
magnitude. 

From February 1 to 11 I have a complete set of estimations. These indicate a 

* See Copernicus, vol. ii. p. 105, for a description of this instrument. 



NEW STAR IN THE CONSTELLATION AURIGA. 53 

maximum about the 7th or 8th. [Compare the curve in fig. 3, and the table on p. 58, 
which have been extended so as to include the subsequent observations.] Not one of 
the four novse of modern times has exhibited a curve of this character, at least as far as 
one can judge from the present available data for Nova Aurigse. 

From Dr Becker I have received the most satisfactory results, derived from observa- 
tions made on February 3, 4, and 5, and again on the 10th and 11th. [These results 
were exhibited to the Society in a graphic form, but it is here preferable to give 
Dr Becker's written account of the observations as received from him on February 16.] 

Observations of the Bright Lines in the Spectrum of Nova Aurigce, 
made at Dunecht by Dr L. Becker. 

The day after the discovery of the new star was announced, I left for Dunecht 
Observatory in order to observe its spectrum with the 15-inch refractor. The large 
spectroscope by Cooke, with a collimator 24 inches in length, having already been 
removed to Edinburgh, I employed in my observations the . smaller spectroscope by 
Grubb, the same with which Professor Copeland had made the greater part of his former 
observations. The collimator of this instrument has 7 inches focal length, and an effective 
pencil of light 0'6 inch in diameter; the viewer is 10 inches in length, and turns by a 
worm-screw with a divided head working against a sector which can be clamped to the 
prism-box. The prism is kept in a fixed position. In these observations a compound 
prism was used at the minimum deviation for b. On the first night, February 3, a power 
of 14 diameters was used, but on the following nights one of 7. For comparison I 
employed the sodium and lithium lines, and the lines of the zinc-lead spark spectrum, as 
produced by a 5 -inch induction coil in connection with a Leyden-jar. The light from the 
spark passes through a lens, and is reflected to the upper and lower part of the slit by a 
small silver mirror, which is fixed in front of the slit and has an opening for allowing the 
light from the object-glass to pass. The same battery which works the coil serves to 
illuminate the field of view by reflection from the last surface of the prism, and also to 
produce bright wire illumination. By means of a small rheostat, which is clamped to 
the sector, the light may be moderated, while a switch enables the observer to put either 
the incandescent lamps or the coil into circuit. This arrangement, which I introduced 
in the last weeks of my stay at Dunecht in 1889, is very convenient if the observer has 
to observe without assistance. In reducing the observations to wave-lengths (Potsdam 
system) I first determined, once for all, 4 constants of Ketteler's formula of dispersion 
from measures of four solar lines equidistant between A and H, and computed a table 
giving the wave-length as a function of the readings of the screw. The deviations of 
this curve from the one given by the observations of solar lines are so small that they may 
be determined with great accuracy by the graphical method. The lines of the spark 
spectrum were measured along with the solar lines, the latter being at the centre part of 
the slit, the former below and above. Although the values of their wave-lengths thus 



54 



PROF. COPELAND AND DR L. BECKER ON THE 



determined are erroneous by the amount of curvature of the lines, they have to be 
employed in the reductions of the star observations in order to reduce the lines of the 
stellar spectrum to wave-lengths. 

In the night observations I measured at the beginning and end of each set the 
prominent spark-lines in the part of the spectrum under observation, always turning the 
screw in such a manner that the viewer moved opposite to the direction of gravity. Their 
readings thus being known, I could then also pick them up while observing the stellar 
lines without being obliged to turn the screw in the opposite direction. The first obser- 
vations serve to correct the reduction-table, the second to determine the changes of 
the zero point. Since the spectroscope is not rigid enough for taking several pointings 
of one line, without observing each time the spark spectrum, I measured through one 
region of the stellar spectrum without turning back. For this reason all the observations 
of any one line are quite independent. Almost all the measures were taken in bright 
field illumination. It is needless to say that the observations of most of the lines were 
very difficult, but I have not the least doubt that those repeatedly observed refer to real 
bright lines, and are not merely an effect of contrast produced by dark lines on the 
continuous spectrum. There are 302 observations, belonging to 71 lines, made on 
February 3, 4, 5, 10, and 11. Afterwards I made arrangements for photographing the 
spectrum, but the sky did not clear up before my return to Edinburgh. 

The mean values of the wave-length A and their intensity I, (where 1 stands for faint, 
6 for very bright) are : — 





Number 










Number 






1892. 


of 
Observations, 


A 


I 




1892. 


of 
Observations. 


A 


I 


Feb. 4, 5, 10. 


5 


657-0 


5 


Feb 


3, 4, 5. 


5 


560-0 


3 


„ 3, 4, 10. 


5 


640-5 


3 


5) 


3, 4, 5. 


6 


5570 


3 


„ 4, 5, 10. 


4 


632-5 


2 


)) 


3, 5. 


5 


552-4 


2 


„ 5, 10. 


2 


624 + 


1 


)) 


4. 


2 


5510 


1 


„ 4, 10. 


3 


620-3 


2 


JJ 


3,4. 


3 


548-8 


2 


„ 3, 5, 10. 


6 


615-1 


2 


)) 


3, 4, 5. 


6 


544-6 


3 


„ 3, 4, 5, 10. 


5 


609-9 


2 


)) 


4. 


1 


543 + 


1 


„ 3, 5, 10. 


7 


604-7 


2 


)J 


4,5. 


5 


540-7 


3 


„ 3, 4, 5, 10. 


7 


598-5 


3 


)> 


5. 


1 


539 + 


1 


„ 3, 4, 5, 10. 


8 


593-4 


3 


>) 


4,5. 


6 


537-4d 


3 


„ 3, 4, 5. 


13 


589-7 + 0-15 


4 


J) 


3, 4, 5. 


6 


533-0* 


4 


„ 3, 4, 5. 


4 


583-8 


1 


JJ 


3, 4, 5. 


5 


528-0 


3 


,, 3, 5. 


3 


5S0-5 


2 


)) 


3, 4, 5. 


6 


524-6 


2 


„ 4,5. 


3 


577-1 


2 


)) 


3, 5. 


3 


519-6 


2 


„ 4,5. 


3 


572-9 


3 


>J 


3, 4, 5, 11. 


8 


517-45 + 0-12f 


5 


„ 3,4,5. 


4 


568-7 


2 


)> 


3. 


1 


513 + 


1 


„ 3, 4, 5. 


4 


564-9 


3 


» 


3, 4, 11. 


4 


511-1 


2 



* Many close lines in this part of the spectrum, of which this is the most prominent. 

t On Feb. 10 it was recorded that the bright line 517-4 is very broad, and that the intensity fell off gradually 
towards the red, while it was cut off abruptly at the more refrangible edge. 



NEW STAR IN THE CONSTELLATION AURIGA. 



55 



Table — continued. 





Number 








Number 






1892. 


of 
Observations. 


A. 


I 


1892. 


of 
Observations. 


A. 


I 


Feb. 3, 4. 


2 


508-2 


2 F< 


sb. 5, 11. 


3 


468-0 


2 


„ 3, 4, 5, 11. 


6 


502-68 + 0-11* 


5 , 


, 5, 10. 


3 


466-8 


1 


„ 4. 


1 


501 + 


2 , 


, 4, 5, 10, 11. 


6 


465-4 


3 


,. 4, 11. 


2 


497-9 


1 


, 5, 10, 11. 


5 


464-3 


3 


„ 3,4. 


2 


494-7 


1 


, 4, 10. 


4 


463-3 


2 


„ 3,4,5,10,11. 


6 


493-17 + 0-17* 


5 


, 5, 11. 


3 


462-3 


3 


„ 3. 


1 


490 + 


1 


, 4, 5, 10, 11. 


5 


460-2 


3 


„ 3,4,5,10,11. 


9 


486-88 + 0-08* 


6 


, 4, 5, 10. 


6 


459-1 


2 


„ 10. 


1 


483-6 


1 


, 4, 5, 10. 


9 


457-8 


3 


„ 3, 4, 5, 10, 11. 


6 


482-0 


2 


, 4,5. 


3 


455-4 


2 


„ 4,5. 


2 


480-7 


2 , 


, 4,5. 


4 


453-8 


2 


„ 3,4,10. 


3 


478-8 


2 


, 4,5. 


3 


451-4 


2 


„ 4, 5, 10, 11. 


6 


477-41 


3 


, 5. 


1 


449-2 


1 


„ 4,5,10. 


4 


475-7 


4 , 


, 5. 


2 


448-0 


2 


„ io. 


2 


474-8 


2 


, 4,5. 


3 


445-5d 


3 


„ 3,4,5,10,11. 


7 


473-7 


4 , 


, 4,5. 


5 


442-1 


4 


„ 10, 11. 


5 


471-7 


3 


, 5. 


3 


439-4 


3 


„ 5, 11. 


2 


470-2 


1 


, 5. 


4 


435-5 


4 


„ 4, 10. 


3 


469-0 


2 











The lines marked d are double. All the measured lines are shown in fig. 1, where 
the fainter grades are indicated by shortening the lines. In fig. 2 an attempt has been 
made to represent the relative intensity of the various parts of the spectrum. 

In the spectrum the Sodium line (D), and the two Hydrogen lines C and F, are 
present; Hy is very probably 435*5, which was just at the limit of visibility. All 
these lines show a decided shift towards the red, from which I find the following velocity 
of the body per second relatively to the solar system : — 

C,+ 211 miles, D,+135(±47) miles, F, 290(±31) miles. 
The very bright line 517*45 lies within the magnesium lines b 1} b 2 , & 4 , and, considering the 
shift of the lines, lies close to the iron lines b 3 , & 4 . However, the great intensity of the 
line compared with that of the other lines of the spectrum, if iron be supposed to be 
present, also the gradual falling away of the light towards the red, are in favour of 
magnesium. The remaining two bright lines are not the nebulous lines. 

As the great intensity of the spectrum in the green, due to numerous lines, many of 
which I was not able to measure, suggests the presence of iron in the Nova, I have entered 
in the second line of the diagram the most prominent lines of the iron arc-spectrum for the 
sake of comparison. Although a number of the lines fall together with those of the Nova, 
one cannot lay much stress upon these coincidences, owing to the great number of lines 
in Iron and the Nova scattered over the whole visible spectrum. 

* It was noted on Feb. 3 that the three lines, 502-7, 493*2, and 486-9, "look as if they are double." On Feb. 4, 
the line 493-2 is entered as the " middle of two lines." 

" Dark spaces between the very bright lines" were seen on every night of observation from Feb. 3 to Feb. 11. 
t More close lines in this place. 



r>6 



PROF. COPELAND AND DR L. BECKER ON THE 



It is noteworthy that some of the brightest lines given above were observed by me at 
Dunecht in the spectra of R Andromedse and R Cygni on October 28, 1889, on an intima- 
tion by the Rev. T. E. Espin that the inline appeared bright in the spectra of these stars. 
Although the observations of these stars could not be completed on account of my remov- 
ing to Edinburgh shortly afterwards, I give the wave-lengths of all the brighter lines in 
their spectra, all of which, it will be seen, agree closely with prominent lines in the spec- 
trum of the Nova. R Andromedse was observed with the slit rather open. 



R Andromedse. 


R 


Cygni. 


Nova Aurigae. 


\ Intensity. 


A 




Intensity. 


A 


Intensity 


... ... 


532-3 




4 


533-0 


4 


528-6 3 


528-9 




3 


528-0 


3 


517-1* 4 


517-0 




4 


517-4 


5 


494-5 4 


...f 






493-2 


5 


486-7 6 


486-0 




6 


486-9 


6 



Postscript added lUh March 1892. 

The new star still continuing bright enough to be observed with the spectroscope, 
I returned to Dunecht on February 24, but was very unfortunate with the weather. 
On March 4 I found that the intensity of the spectrum had much decreased, but that the 
bright lines were still easily seen. From C to 550 I again measured all the brighter lines, 
while between 550 and FI obtained almost every line that is given above. Thirty-eight 
lines in all were re-measured, but the results are not combined with those already given. 
Beyond F the light was too faint for measuring. The results agree with the earlier ones 
as closely as the size of the spectroscope entitles one to expect. The power 14 was 
employed. The intensity of some of the lines relatively to each other appeared to be 
changed. Certainly F was no longer the brightest line, the line 5 17 '5 considerably sur- 
passing any of the others. I was not able to detect any narrow dark lines which had been 
announced in the meantime, but I measured the middle of the dark spaces to the violet 
of some of the brightest lines, which formerly I had attributed to the effect of contrast. 
The wave-lengths of the brightest lines in the green-blue, and their relative intensities 
(the brightness in February is given in parentheses), were observed as follows : — 



Number of 








Observations. 


X 


Intensity. 


Remarks. 


2 


533-4 


4 (4) 




2 


528-7 


4 (3) 




2 


524-6 


4 (2) 




2 


517-5 


6 (5) 




2 


502-7 


5 (5) 


Breadth, 0"5. 


1 


501-2 




Middle of dark space ; breadth, 2'0. 


3 


493-0 


4 (5) 


Dark bands to the red and violet. 


5 


487-1 


4 (6) 




1 


484-8 




Middle of dark space ; breadth, 3 '6. 



* A companion on either side l^mmm- off. 

t One very bright line missed (according to note-book) near .F towards the red. 



NEW STAR IN THE CONSTELLATION AURIGA. 57 

Further Remarks on Nova Aurigce. By Professor Ralph Copeland. 

(Communicated 21st March 1892.) 

The most remarkable additional fact that I have to communicate is a sudden diminu- 
tion in brightness that seems to have set in about the 7th of March. Throughout the 
month of February the Nova exhibited continual and irregular changes of brightness, 
which are shown by the dots in the diagram. The state of the sky was unusually 
favourable during the earlier part of February, and later on still offered occasional 
opportunities of comparing the star with its neighbours. Unfortunately, on March 8, 
I had the misfortune to lose the very fine binocular that had up to that time been used 
in these observations. Hoping that it might be recovered, and not apprehending that 
any very surprising change in the star's brightness was about to occur, I did not attempt 
to replace it until the 13th, when, on examining the heavens with a good opera-glass, I 
was unable to identify the star. It was, however, readily found with a 35-inch refractor, 
but had declined to the 8*6 magnitude. [See figure 3, and the table on p. 58.] On the 
19th it had lost a further ,m 3, while last night it had so far faded as only to be of the 
9"1 magnitude. We thus see that on February 7 the Nova was about 132 times as 
bright as it was last night. Its brightness on the 8th and 20th are in the ratio of 14 
to 1. 

Last night, March 20, Nova being about one magnitude brighter than the small star 
close to it, which was observed at Bonn 34 years ago, it was still practicable to analyse 
its light with the small spectroscope. The spectrum was strongly continuous in the 
yellow, green, and blue, with several intenser parts that probably represented bright lines. 
No trace of the bright C line, formerly so conspicuous, could be made out. It does not 
seem, at present, that the spectrum is likely to become reduced to a single bright line as 
was the case with the Nova of 1876, but it seems rather to resemble the continuous 
spectrum of Nova Coronse, as it appeared in 1866, when the bright lines were superposed 
on the continuous spectrum. 

Note added April 17. 

The further history of this star, as seen in the Edinburgh reflector, is one of steady 
and continued decline. The magnitudes on the days of observation are given below 
until April 1, when it was seen for the last time. The place was examined in a hazy 
sky on April 14, and again on the 18th, when the night was clear, with the exception 
of a little inevitable smoke ; on neither of these occasions was a trace of the star dis- 
cernible. Its spectrum was " continuous with traces of dots " on March 25, the star being 
estimated of the 107 magnitude. The brighter magnitudes have been apportioned in 
accordance with the Durchmusterung and some Harvard measures. The fainter part 
of the scale has been formed on the assumption that the " Bonn star " is 9 ,m 9, while the 



•- 



PROF. COPELAND AND DR L. BECKER ON NEW STAR IN AURIGA. 



small star, which forms an equilateral triangle with it and the place of the Nova, is set 
down as 12 ,m 7. 

On March 28, when it had fallen to ll ,m 9, it could no longer be seen through a 
prism which gave a distinct spectrum of the neighbouring 9 ,m 9 Bonn star. Hence we 
may certainly conclude that on this day the light of Nova Aurigae was far from 
monochromatic, or it would have been visible through a prism. 

Observed Magnitudes of Nova Aurigce. 



Day. 


Hour. 


Magnitude. 


Comparison Stars and Remarks. 


Instrument. 


1892. 


h 








Feb. 1. 


6.1 


5-56 


26 Aurigae ; Nova strong yellow. Image strictly 
stellar afterwards in the 24-inch telescope. 


F.G. 


2 


8.1 


556 


26. Nova seen with naked eye. 


»> 


„ 3. 


9.4 


513 


26 and x Aurigae. 


5) 


„ 4. 


8.1 


5-0 


X- 


>) 


„ ,5. 


7.3 to 9.8 


465 


26 and x- 


)> 


„ 6. 


6.5 and 7.8 


4-55 


X- 


)) 


„ 7. 


12.0 


3-80 


X ; moon very near ; Nova seen with unaided eye. 


)) 


„ 8. 


6.0 and 11.1 


4-09 


26 and x- 


)) 


„ 9. 


7.8 


5-03 


26 and %. 


>> 


■ „• io. 


8.8 and 11.1 


5-0 


26 and x- 


)> 


„ 11. 


10.0 


5-0 


X 


)> 


„ 16. 


8.3 and 8.8 


5-87 


26 and D.M. + 30° 898. 


O.G. 


„ 17. 


6.9 to 12.2 


5-43 


26, 898, and x> Nova certainly brighter than last 
night. 


F.G. 


„ 18. 


7.8 to 12.4 


5-38 


26 and x- 


») 


„ 19. 


8.3 and 9.2 


5-10 


X- 


)> 


„ 22. 


11.1 


576 


X- 


>> 


„ 29. 


7.9 


5-76 


26. 


j> 


Mar. 5. 


9.6 


5-58 


X- 


)! 


v 8 - 


9.7 


6-26 


26. 


O.G. 


„ 18. 


8.9 and 9.3 


8-58 


D.M. + 30° 912 and 913. 


3|in. 


» 19. 


9.8 


8-9 


913 and + 30° 932. 


>> 


„ 20. 


9.0 and 9.5 


9-1 


913, 932, and Bonn star of 1858. 


3| and 24 in. 


„ 23. 


9.4 


9-7 


Bonn star. 


24 in. 


„ 24. 


11.6 


100 


Bonn star. 


n 


» 25. 


10.8 


10-7 


Bonn star and p * of a pair sf= f . 


" 


„ 28. 


8.7 


11-9 


f and faint star of triangle = g. 


" 


„ 29. 


9.0 


12-4 


g- 


" 


,, 30. 


9.0 


12-6 


g- 


" 1 


Apr. 1. 


9.1 


12-9 


g and next * to s. 


" 



The instruments used were F.G., a large field-glass ; O.G., two different opera-glasses ; 
a 3^-inch refractor by Cooke, with a power of 27 ; and, lastly, the 24-inch Grubb reflector 
and a power of 138. The silvering of the last-named instrument is at present somewhat 
thin and imperfect. 






SPECTRUM, INTENSITY-CURVE AND MAGNITUDES OF NOVA AURIGA, 1892. 

Trans. Roy. Soc. Edin. Vol. XXXVI 




( 59 ) 



V. — The Lateral Sense Organs of Masmobranchs. I. The Sensory Canals of 
Leemargus. By J. C. Ewaet, M.D., Regius Professor of Natural History, 
University of Edinburgh. (Plates I. and II.) 

(Read 6th July 1891.) 

Introductory. 

Some years ago, when studying the electrical organs of' the torpedo, I was forced to 
the conclusion that the nerves supplying the batteries had not been accurately described, 
and that notwithstanding the statements in the most recent works, the first electric nerve 
is not derived from the trigeminus. Finding some difficulty in making out the arrange- 
ment of the cranial nerves in the greatly specialised torpedo, I directed my attention, 
first to the skate, and later to certain sharks, more especially to the Greenland shark 
(Leemargus). I had not proceeded far before I was convinced that we had still much to 
learn as to the anatomy of the cranial nerves of both the higher and lower vertebrates. 

Up to a certain point I made satisfactory progress, and early in March 1889 was in 
a position to communicate to the Eoyal Society a preliminary paper " On the Cranial 
Nerves of Elasmobranch Fishes " (1) ; and, in the following year, papers on the cranial nerves 
of the torpedo (2) and on the development of the ciliary ganglion (3). When, however, I 
endeavoured to interpret my results, more especially when I endeavoured to compare the 
cranial nerves in Selachians with those of the higher vertebrates, innumerable difficulties 
presented themselves. After full consideration, there seemed only two possible lines 
along which further progress was possible. The one was to study anew the development 
of the cranial nerves in two or more vertebrate groups ; the other to make a special 
study of the innervation of the more important organs peculiar to fishes. 

Many able investigators having already directed their attention to the development 
of the nervous system, without, it must be confessed, arriving at any very generally 
accepted conclusions, I ventured to think that, with the help of the embryological facts 
already established, I would best succeed by trusting mainly to the old methods of the 
comparative anatomist. I believed that, by a careful study of the conditions in the adult 
Selachians, certain morphological questions would be settled, and that a new base of 
operations might be opened up for the embryologist. Hence, instead of publishing the 
views I entertained as to the relation of, e.g., the complex facial of the Selachian, with its 
comparatively simple homologue in the higher vertebrates, I decided to first thoroughly 
work up the lateral sense organs — structures which reach a remarkable development in 
fishes, but are entirely absent in the higher vertebrates. In this way I hoped to 
determine which of the many large and well-marked nerves of the fish we should expect 
to find absent in Sauropsida and Mammalia. 

VOL. XXXVII. PART I. (NO. 5). L 



60 PROFESSOR J. C. EWART ON THE 

This plan necessitated the delay of any lengthened discussion of the cranial nerves, 
and the breaking up of the work into a number of more or less independent investiga- 
tions. Now that the work has advanced towards completion, I am satisfied that the 
best plan was adopted. When I originally discovered four ganglia in connection with 
the facial in the fish, I was inclined to believe that I ought to find their counterparts in 
other vertebrates, and at once set about preparing schemes with a view to establishing 
their relationships. By a roundabout process, however, I now know that there is no 
necessity, in many cases, to look in the adult higher vertebrates for even the vestiges of 
some of the nerves largely developed in fishes. 

As the optic and olfactory nerves dwindle or disappear when their related organs are 
in a vestigial condition or absent, so some of the ancestral ganglia and nerves have 
disappeared as their organs (only useful for an aquatic life) have degenerated. Prepared 
for the complete absence of various nerves the work has been simplified, and time saved 
which might have been wasted in making impossible comparisons. Now that the whole 
ground has been roughly worked over, I propose, first, to describe the lateral sense 
organs in several fishes, paying special regard to their innervation. This done, I shall 
describe fully the cranial nerves in two or more members of the Elasmobranch group ; 
and, finally, complete the work by making a comparative study of the cranial nerves of 
the more important divisions of the vertebrata. 



THE LATERAL SENSE ORGANS. 
I. Historical. 

In Elasmobranchs, the lateral sense organs consist of two distinct systems of canals, 
and, in addition, of minute pit organs or follicles. Hitherto, the two kinds of canals 
have usually been known as mucous canals ; but as they differ in structure and arrange- 
ment, and, perhaps, also in function, distinctive names are obviously necessary. The 
canals of the one system open on the surface of the skin by numerous usually short and 
simple tubules ; and they further, in some cases, give off long branches, also provided 
with tubules. The canals of the other system radiate from a given number of centres in 
the head region ; and each canal presents an expansion (ampulla) at its proximal end, 
and opens on the surface of the skin by its distal end. These radiating canals, however, 
though often running a considerable distance side by side, never communicate with each 
other ; nor do they give off tubules or branches. 

The canals with tubules, which include the canal of the lateral line and a number of 
canals in the head region, I have, for various reasons, decided to speak of as the Sensory 
Canals. They are not only characterised by their tubules and branches, but also, and very 
specially, by the presence of numerous sense organs — structures which are present when 
the tubules are absent, and when grooves or furrows take the place of the canals. The 
canals without tubules and branches I shall invariably refer to as Ampullary Canals, 



SENSORY CANALS OF L^EMARGUS. 61 

chiefly because they are especially characterised by the ampullae at their proximal ends — 
the ampulla? of Lorenzini. 

In Laemargus, according to the nomenclature I have adopted, there are three main 
canals in the head region and one in the trunk — the cranial canals having over 
four hundred sense organs, and a nearly corresponding number of tubules. The 
ampullary canals, though numbering over one thousand, will be found to radiate from 
four centres, all situated in the head region. Having indicated the main features of 
the two canals, and the names by which they will be described, I need only further say, 
before referring to the history of the subject, that sensory follicles have not yet been 
found in Laemargus. 

The first observations relating to the lateral sense organs of fishes seem to have been 
made by Stenonis, who, in 1664, described certain openings in the skin of the skate for 
the discharge of mucus (4) ; and, in 1669, discovered similar openings in a shark (5). 
About ten years later (1678), Lorenzini (6) not only found the openings described by 
Stenonis, but made the important discovery that the openings belonged to two kinds 
of canals (the sensory and ampullary canals mentioned above), and especially noted the 
expansion (ampulla) at the proximal end of each of the simple (ampullary) canals. 

Since the time of Lorenzini, many anatomists and zoologists have studied the 
" mucous " canals of fishes ; but Lorenzini's discovery that the canals were of two 
kinds has been too often overlooked ; and it was not until 1813 that it was first suggested 
these canals played any other part than that of secreting and distributing mucus over 
the surface of the skin ; and not until 1868 that their right, from a morphological point 
of view, to be considered sensory structures was finally established. 

Very little progress was made in working out the structure of the lateral sense organs 
from the time of Lorenzini to that of Monro secundus, who* in the latter half of the 
eighteenth century, worked at " The Structure and Physiology of Fishes " (7). Monro 
especially directed his attention to the " mucous " canals of the skate, and he made out 
(what seems to have escaped the notice of Lorenzini) that large nerves proceeded to the 
gland-like masses (groups of ampullae) formed by the inner ends of what I have termed 
the ampullary canals. There is no evidence, however, that Monro was acquainted with 
Lorenzini's work or that he recognised the difference between the branched (sensory) and 
simple (ampullary) canals, or specially observed the ampullae of Lorenzini ; and though 
he traced large nerves to the central masses, he apparently considered the canals as mere 
mucus-producing structures. He describes them as "very elegant structures for the 
preparation of mucus for keeping moist the surface of the skin." Nevertheless, Monro's 
noting that large nerves reached the central masses (the groups of ampullae) may have 
helped Jacobson, in 1813, to arrive at the conclusion that the mucous canals of sharks 
and rays were sensory organs (8). 

During the first half of the present century, the lateral sense organs attracted the 
attention of several investigators besides Jacobson, more especially St Hilaire, 
Treviranus, de Blainville, Della Chiaje, Savi, Mayer, and Robin. The central 



62 PROFESSOR J. C. EWART ON THE 

masses (groups of ampullae) which Jacobson considered sense organs, St Hilaire (1801) 
described as electric organs (9), and this extraordinary mistake was also made by Mayer 
(10) (1843), Jobert de Lamballe (11) (1858), and M'Donnell (12) (1861). As early as 
1822, Blainville (13) pointed out St Hilaire's mistake; and Eobin (14) and several 
others have confirmed the observations of Blainville, as to the correctness of which there 
can no longer be any doubt, notwithstanding M'Donnell's statements to the contrary. 
Unfortunately, Mr Darwin refers to M'Donnell's observations, and remarks, in the 

Ongin of Species (p. 150, 6th edition) : — "In the Ray there is an organ near 

the head, not known to be electrical, but which appears to be the real homologue of the 
electric battery of the Torpedo." M'Donnell's homologue of the torpedo's battery, 
which exists in sharks, as well as rays, will be afterwards described as the hyoid group 
of ampullae. 

Trevlranus (15), who was one of the first to describe the central masses (ampullary 
groups) in sharks, considered them as sensory structures. Savi (16), Robin, and others, 
followed Jacobson and Treviranus ; while Della Chiaje (17), probably unacquainted 
with Jacobson's work, like Monro, considered the mucous canals as simply concerned in 
the secretion of mucus. 

But little real progress was made until Leydig and H. Muller directed their attention 
to the subject. Leydig's first paper appeared in 1850 (18); but it was not until 1868 that 
he published a full account of his observations. Leydig's monograph ( Ueber Organe eines 
sechsten Sinnes) is by far the most important work that has hitherto been published on 
the lateral sense organs of fishes (19). The author points out that, from the morphologist's 
standpoint, not only the mucous canals — the sensory and ampullary canals — but also 
the peculiar little follicles found in the torpedo by Savi, are all sensory organs. They 
were together regarded by Leydig as the organs of a sixth sense. 

H. Muller, like Leydig, considered the follicles of Savi, as well as the two forms of 
mucous canals (sensory and ampullary), as concerned in sensation rather than in secre- 
tion. His observations (20) were published seventeen years before the important memoir 
by Leydig. Kolliker (21) and Max Schultze (22), prior to 1868, had pointed out the 
existence of sensory cells in the follicles of Savi. 

Since 1868, amongst others who have worked at the lateral sense organs of fishes, 
may be mentioned Boll, Goette, Semper, Balfour, Sappey, Beard, Garman, Allis, and 
Fritsch. Boll (23) refers especially to the structure of the ampullae and their canals. 
Goette (24), Semper (25), Balfour (26), and Beard's (27) work relates chiefly to the 
development of the canals and their nerves ; while Sappey's (28) work is, in a manner, 
an extension of the investigations of Monro. Garman (29), who studied the canals 
chiefly with a view to ascertaining their value in classification, shortly describes and 
figures their arrangement in a large number of sharks and rays ; while Allis (30) gives 
an able and exhaustive account of the lateral line system in Amia. Fritsch (31 and 32) 
deals with the canal system in the Selachia as a whole, and also describes shortly the 
lateral sense organs of the torpedo, and peculiar little follicles (syalt-papillen) which he 



SENSORY CANALS OF L^MARGUS. 63 

discovered in the skate. Notwithstanding what has already been done, there does not 
yet exist a complete and systematic account of the lateral sense organs of a single 
Elasmobranch. As pointed out by various writers, the general anatomy of the canals 
has been strangely neglected. When studying the sensory canals of Selachians, we have 
still to fall back on the very meagre account of these structures given by Monro, or the 
more elaborate, but in many respects unsatisfactory, work of Sappey. 

II. Development and General Anatomy. 

Eecent work on the origin and development of the nervous system of vertebrates has 
necessitated, more than ever, a full account of the structure and general distribution of 
the sensory canals in both sharks and rays, and especially of an accurate description of 
their innervation. 

Now that the origin and distribution of the cranial nerves — more especially of the 
trigeminal and facial — are better understood, and that the sensory canals have been 
shown to be at the outset intimately related to certain cranial ganglia, we are in a 
position to study their anatomy with the prospect of obtaining more valuable results 
than was possible even a few years ago. 

Although both systems of canals have reached a remarkable development in many 
fishes, and sensory canals or furrows with well-developed sense organs exist in nearly all 
fishes, it has not yet been possible to determine the function of either the sensory or 
ampullary canals. Not only is the use of the lateral sense organs still a mystery, but 
also very little is known as to their development in Elasmobranchs. From what is 
known, it appears to me that, in describing the. canals, special attention should be given 
to their innervation. According to Beard (27), an epiblastic thickening is found in young 
embryo Selachians over each visceral cleft. Towards this thickening the dorsal root of a 
cranial nerve grows outwards from the neural crest, reaching and blending with it on a 
level with the notochord. Where the fusion takes place, the cells proliferate and give 
rise to the rudiment of a cranial ganglion, and, more superficially, to the rudiment of a 
lateral (branchial) sense organ. After a time, a separation takes place ; and, eventually, 
the deeper group of cells gives rise to a ganglion, while the superficial gives rise to the 
sense organ. A connection between the ganglion and the sense organ is maintained by 
a nerve (the dorsal or supra-branchial nerve), which is split off from the under surface of 
the epiblastic thickening as development proceeds. Though, by division and growth in 
different directions, the original simple sense organ may become complex, the dorsal 
nerve and its branches maintain a connection between the sense organs and their related 
ganglion. 

Taking these and other observations into consideration, together with what has 
recently been made out as to the innervation of the sensory canals in Lsemargus and 
Raia, it appears that, while the lateral canal of the trunk in Elasmobranchs has been 
formed in connection with a backward growth of the lateralis division of the vagus, the 



64 PROFESSOR J. C. EWART ON THE 

principal cranial canals have been formed in connection with three extensions of the 
facial — two forwards and one outwards. One of these divisions of the facial (the 
ophthalmicus superficialis) has grown forwards above the eyeball, another (the buccal) 
has grown forwards under the eyeball, and the third (the hyomandibular) outwards and 
forwards behind the spiracle. The three canals in relation with these nerves should have a 
corresponding position ; one should run forwards above the eyeball, one curve downwards 
and forwards below the eyeball, and a third should lie behind the spiracle. 

If we turn to Lsemargus we first of all notice, all over the head, but especially above 
and below the snout, a large number (over 1500) of small but perfectly distinct pores. 
The majority of the pores have the margin slightly projecting and deeply pigmented. 
Without much difficulty it becomes evident that some of the pores serve as openings 
for ampullary canals ; while others lead by short tubules into sensory canals. If the 
arrangement of the openings of the sensory tubules is studied, or if the canals from which 
the tubules spring are exposed, it will be found that, as expected, one canal extends 
above, while a second lies below the eyeball. The first, which is related to the 
ophthalmicus superficialis nerve, maybe known as the supra-orbital canal (S.O., figs. 1 
and 2). The second, which is related to the buccal nerve, may be known as the infra- 
orbital (I.O., figs. 1 and 2). But although the canals of the ophthalmic and buccal 
divisions of the facial are easily recognised in Lsemargus, there is some difficulty 
in distinguishing the canal related to the hyomandibular division. This canal, though 
not at first evident in Lsemargus and other Selachians, is easily distinguished in the 
ganoid Amia. By referring to figure 3 (PI. II.), a canal (HM.) as complete and distinct 
as the infra-orbital (I.O.) will be seen beginning on the same level as the infra- orbital, 
and extending downwards and forwards along the mandible. This canal is supplied 
throughout its entire length by the hyomandibular division of the facial, and it has the 
same relation to the hyomandibular as the infra-orbital canal has to the buccal division 
of the facial. 

I propose to call this canal the hyomandibular canal. Allis (30) describes it as the 
operculo-mandibular ; but this name could not well be used for either sharks or rays, in 
which, though the lower part of the canal is usually more or less complete, the proximal 
part is never, so far as I know, present. 

In the remarkable fish Chlamydoselachus (33), the mandibular portion (0.), as shown 
in figure 4, is complete, and, in addition, there is an extension forwards (ang.) to join 
the infra-orbital and another backwards (j.) over the operculum, which bifurcates near its 
margin, one division running upwards and forwards (sp., fig. 5), the other downwards 
and forwards {g., fig. 4), to join the mandibular portion. 

In Lsemargus, the lower (mandibular) as well as the upper part of the hyomandi- 
bular canal is absent ; and the only representative of the long canal of Amia is a short 
horizontal canal (HM., fig. 1, PI. I.) which runs backwards from the infra-orbital, external 
to a well-marked fold of skin at the side of the mouth. 

That this short canal belongs to the hyomandibular and not to the infra-orbital, 



SENSORY CANALS OF L^MARGUS. 65 

is clearly indicated by its being innervated by the hyomandibular branch of the 
facial. 

In addition to these three main cranial canals and the lateral canal of the trunk, 
there are in Laemargus only two other canals : — (1) a canal (I.e., fig. 1, PI. I.) which 
lies behind the auditory pores and serves to connect the canal systems 'of the two sides 
(as this commissural canal is innervated by the lateralis nerve, it will be considered as 
part of the lateral canal) ; (2) a short canal (p,L, fig. 1, PI. I.) continuous with the 
lateral canal, which seems to form its most anterior portion, but as it is innervated by 
the buccal branch of the facial nerve, it will be looked upon as belonging to the infra- 
orbital canal. It thus appears that in Laemargus all the sensory canals are supplied by 
two nerves — the vagus and facial, or to be more explicit, by the lateralis division of the 
vagus and the ophthalmic, buccal, and hyomandibular divisions of the facial ; and hence 
we might speak of the ophthalmic, buccal, hyomandibular, and lateral sensory canals. 

Hitherto in Selachians, the sensory (mucous) canals have been studied per se, with the 
result that an extremely complicated nomenclature has arisen. For example, Garman (29), 
who refers shortly to Laemargus under the name of Somniosus carcharias, indicates the 
presence of fourteen cranial canals. In doing this he follows the system of Agassiz and 
most other writers, and practically takes no heed of the relation of the canals to the 
cranial nerves, as has been recently done to a considerable extent by Allis in his descrip- 
tion of Amia. From the statement of Garman, in his introductory chapter, that the 
canals on "the head are innervated mainly from the fifth pair," it may be inferred that 
he has not directed his attention specially to the nerve-supply of the canals ; the fifth, as 
I have already indicated, taking no part in innervating the canals. To admit of the old 
and complex nomenclature being compared with the simpler one I propose to use, I have 
reproduced Garman's figures of Laemargus (Somniosus — woodcuts A and B), and will in- 
dicate, as I proceed, which of his canals correspond to the cranial canals I have already 
mentioned, viz., the supra- and infra-orbital and hyomandibular canals. 

In referring to the development of the lateral sense organs, it was mentioned that 
while the superficial portion of each epidermic thickening gives rise to the rudiment of a 
branchial sense organ, the deep portion assists in forming a cranial ganglion. According 
to Beard (27), there should be in a typical Selachian seven dorsal (supra-branchial) nerves, 
and a corresponding number of sense organs — i.e., (1 and 2) an ophthalmicus profundus 
and an ophthalmicus superficialis of trigeminus in connection with sense organs over the 
snout ; (3 and 4) an ophthalmicus superficialis of facial in connection with the supra- 
orbital, and a ramus buccalis of facial in connection with the infra-orbital sense organs ; 
(5 and 6) the glossopharyngeus and anterior vagus branches in connection with the supra- 
temporal sense organs ; and (7) the nervus lateralis of vagus with the organs of the 
lateral line. Whether this supposed typical arrangement obtains in embryo SelachiaDS 
remains to be seen ; but I have not found that Beard's scheme holds for either fully 
developed sharks or rays, and according to Allis it does not hold in the case of Amia. In 
Amia, Allis states that " the trigeminal and ophthalmicus profundus take no part with 



66 PROFESSOR J. C. EWART ON THE 

any of their branches in the innervation of the canals or pit organs," and that " there is a 
large and important operculo-mandibular line of organs," in the innervation of which 
none of the supra-branchial branches given in Beard's scheme take any part (30). 

. These statements as to Amia apply also to Lsemargus, and the only essential difference 
in the innervation of the canals in the two, in many respects, diverse forms, is that in 
Lsemargus I have not succeeded in finding a branch from the glossopharyngeal nerve to 
any of the sense organs. 

In view of the statement that the embryonic epidermic thickening assists in forming 
a cranial ganglion as well as a branchial sense organ, it is worth specially noting that 
each of the four nerves which sends branches to the sensory canals, i.e., the ophthalmicus 
superficialis, buccal, and hyomandibular divisions of the facial, and the lateralis 
division of the vagus, presents some distance from its origin a well-marked ganglionic 
swelling crowded with large nerve cells. In the skate these ganglia are relatively as 
large as or larger than the ganglia on the profundus, trigeminal, and glossopharyngeal 
nerves — nerves which in adult sharks and rays have not yet been found in connection 
with lateral sense organs. It is further worthy of note that the buccal and superficial 
ophthalmic ganglia are sometimes in contact with each other by their proximal ends. 
From this it might be inferred that there has been a splitting of the original epidermic 
thickening above the spiracular cleft, the splitting resulting not only in the formation 
of two ganglia, but also of two sensory canals — the supra-orbital above, and the infra- 
orbital below, the eyeball. 

III. The Sensory Canals of Lsemargus. 

The position of the four main canals already mentioned is indicated by their names. 
The supra-orbital canal (S.O., fig. 1, PI. I.) begins some distance in front of the auditory 
pores and extends forwards towards the tip of the snout, which it perforates, and then 
runs backwards to unite with the infra-orbital as it bends inwards towards the middle 
line. 

The infra-orbital (less the accessory otic portion ; I.O., fig. 1), beginning in connection 
with the supra-orbital, runs outwards behind the eyeball, and then forwards between the 
eyeball and the mouth, and after communicating with the supra-orbital it bends inwards 
and forwards towards the tip of the snout. 

The hyomandibular (HM., fig. 1), communicating in front with the infra-orbital, runs 
backwards in a nearly horizontal direction. 

The laterals (L., fig. 1) continuous in front with the otic portions of the infra- 
orbitals, after communicating with each other behind the auditory pores, run almost 
directly backwards, one at each side of the trunk, until on a level with the posterior 
margin of the lower lobe of the caudal fin, when they bend upwards to terminate on the 
upper lobe of the fin, one at each side of the terminal portion of the vertebral column. 

1. TJie Supra-orbital Canal. — This, the canal of the superficialis ophthalmicus 



SENSORY CANALS OF L^MARGUS. 



67 



division of the facial, represents the cranial (cr.), rostral (r.), and subrostral (sr.) canals 
of Garman (tigs. A and B). Garman figures and describes the cranial (first portion of 
the supra-orbital) as beginning in front of, and distinct from, the orbital (orb., fig. A), i.e., 
the first portion of infra-orbital. This view I was at first prepared to accept ; but on 
cutting into the canals, I found that they not only communicate with each other, but 
open to the exterior by a common pore. 

The course of the supra-orbital canal will be best understood by a reference to 
figure 1 (PL I.). Beginning 3*25 cm.* in front of the auditory pore, and 1 cm. from the 
middle line, it first bends outwards and forwards, and then forms a wide open curve 
(S.O. 1 ), within which lie the openings of numerous ampullary canals. 

On approaching the region of the nasal capsule, the canal runs inwards and then 
forwards to perforate the snout, about 2^ cm. from the middle line, and 1 cm. behind its 
anterior margin. Turning sharply backwards, it runs outwards, and then returns to the 
dorsal aspect (S.O. 3 ), arching over the nasal capsule to again reach the ventral surface ; 
where, after curving first inwards and then outwards, it terminates (S.O. 4 ) by communi- 
cating with the infra-orbital canal (I.O. 2 ). 




The supra-orbital canal has, throughout the greater part of its length, a diameter of 
from 3 to 4 mm. ; but the first 3 or 4 cm., and the portion which curves over the 
nasal capsule, are only from 2^ to 3 mm. in diameter. The walls of the canal are from 1 
to 1| mm. in thickness. The canal not only varies in diameter, but also in its relation 
to the skin. Some parts lie in contact with the skin ; while others lie embedded, some 
distance from the surface, in the subcutaneous tissue. Usually, the portions in contact 
with the skin have a smaller calibre than the portions lying deeper. Beginning in 
contact with the skin, the canal, when about 3 cm. from its origin, sinks to a distance of 
4 mm. When on a level with the nasal capsule, it lies 6 mm. from the surface ; and the 

* The measurements refer throughout the paper to a fish that had a total length of 11 feet. 
VOL. XXXVII. PART I. (NO. 5). M 



68 PROFESSOR J. C. EWART ON THE 

depth rapidly increases as it runs forwards to perforate the snout. The ventral portion 
lies at an average depth of 5 mm. ; but the part in front of the snout is deeper, while 
the part over the nasal capsule is immediately under, or actually embedded in, the skin. 
The supra-orbital canal contains numerous sense organs, and is perforated by two rows of 
pores or apertures, an inner row for the nerves which reach and end in the sensory 
hillocks, and an outer row of larger apertures, which lead into the tubules by which the 
canal communicates with the exterior. The sense organs and tubules are shown on the 
right side of figure 1. 

Eighty-three tubules, and a corresponding number of sense organs, were found in the 
supra-orbital canal of the specimen examined. Each organ received a delicate branch 
of the ophthalmicus superficialis nerve, the nerves entering by the minute pores nearly 
opposite the inner ends of the tubules. 

The length of the tubules varies almost constantly with the distance of the canal 
from the surface. Some of them are under 2 mm. in length, while others are nearly 
1 cm. The majority of the tubules run obliquely outwards ; but a number proceed from 
the outer surface of the canal directly through the skin. The openings of the tubules 
are from 1 to 1'5 mm. in diameter ; and the outer 2 or 3 mm. are distinctly pigmented. 
The openings of the tubules are readily distinguished from the openings of the ampullary 
canals. They are more regular in their arrangement than the openings of the ampullary 
canals, and the margins are usually more deeply pigmented. 

By comparing the supra-orbital canal of Lsemargus with that of Chlamydoselachus 
(cr., r., sr., figs. 4 and 5), it will be noticed that it differs in several respects. Not only 
is it not in a line with the lateral canal as is the case in Chlamydoselachus, but it neither 
directly nor indirectly communicates with this canal ; and, further, unlike all the ordinary 
Selachians, it returns to the dorsal surface of the snout as it proceeds backwards to join 
the infra-orbital. This return to the dorsal surface seems to be due to the nasal opening 
occupying a more outlying position than is usually the case. Posteriorly, the two supra- 
orbitals bend inwards towards each other, and thus approach the arrangement in the 
Holocephala, in which the connection between the canals of the two sides is accomplished 
by the union of the supra-orbitals instead of the union of the laterals behind the auditory 
pores. 

Innervation of the Supra-orbital Canal. — The nerve (the superficial ophthalmic of 
facial (s.o.f., fig. 1) of the supra-orbital canal gives off branches as it runs forwards over 
the eyeball to the first (cranial) part of the canal. On reaching the nasal capsule, it 
sends a branch downwards and outwards (s.of. 2 ,"B.g. 1) to supply the sense organs of the 
ventral part of the canal ; and, then, as it passes forwards towards the end of the snout, it 
gives off twigs for the sense organs in the part of the canal in front of the nasal capsule. 
A more detailed account of the innervation of this and the other canals will be included 
in a paper, in course of preparation, on the cranial nerves of Lseniargus. 

2. The Infra-orbital Canal. — This canal (I.O.-I.O. 5 , fig. 1), as already mentioned, 
communicates at its origin with the supra-orbital. From the common opening it runs out- 



SENSORY CANALS OF LJEM ARGUS. 69 

wards nearly at right angles to the long axis of the head, and passes downwards behind 
the orbit. Having reached the ventral aspect, it communicates with the hyomandibular 
canal (HM., fig. l), and then bends forwards and inwards to meet and communicate with 
the supra-orbital canal (S.O. 4 , fig. 1), as it turns sharply inwards towards the middle line. 

On the way it forms a characteristic forward projecting loop (I.O. 3 , fig. 1). On reach- 
ing the middle line it blends, for a short distance, with the corresponding canal of the 
opposite side (I.O. 4 , fig. 1). Leaving its fellow it runs outwards and forwards to sink 
well into the substance of the snout, and terminate blindly about 6 mm. from its anterior 
margin, and 1^ cm. from the middle line (I.O. 5 , fig. 1). This canal corresponds to the 
orbital (orb.), suborbital (so.), orbito-nasal (o.n.), nasal (n.), median (half of) (m.), and 
prenasal (pn.), canals of Garman (figs. A and B). 

In diameter the infra-orbital resembles the supra -orbital. Narrow at first, it 
gradually widens until it reaches the side of the head, where it contracts slightly, to 
again expand as it reaches the under surface. With the exception of the median and 
terminal portions, the ventral part of the canal has a diameter of from 3 to 4 mm. 

The median portion is from 5 to 6 mm. wide, while the terminal portion varies from 
2 to 3 mm. The canal, at first in contact with the skin, soon sinks to a depth of 5 mm., 
but on reaching the level of the spiracle it again approaches the surface and remains all 
but in contact with the skin until it joins the hyomandibular. Between this canal and 
the supra-orbital, it lies at a depth of nearly 5 mm. ; but as it bends inwards it becomes 
more superficial, lying at a depth of 3 mm. until it reaches the under surface of the 
rostrum, where it sinks to a depth of 5 or 6 mm., and finally, at its termination, to a 
depth of 1 cm. 

Eighty-seven twigs from the buccal nerve were found penetrating this canal to reach 
and end in a corresponding number of sense organs. Of these nerves there were 24 in 
the first part of the canal (orbital and suborbital), 11 in the second (orbito-nasal), 23 in 
the third (nasal), 3 in the common median part, and 26 in the terminal (prenasal) part. 
The nerve pores varied considerably in their arrangement ; near each other at first, they 
became less numerous in the descending part of the canal, after which they were fairly 
regular with the exception of the anterior (prenasal) part, in which they were especially 
abundant. The distribution of the fibres of the buccal to the nerve hillocks is indi- 
cated on the right side of figure 1. 

This canal opens through the skin by tubules similar to those of the supra-orbital. 
Altogether 86 tubules were counted, and, as a rule, they proceeded from the canal 
opposite the pores for the entrance of the nerves. The majority of the tubules varied in 
length with the distance of the canal from the surface ; the dorsal tubules extended 
backwards ; the majority of the ventral directly outwards ; but those from the terminal 
portion of the canal projected outwards and forwards. The irregular ventral part of the 
infra-orbital canal comes into intimate relation with numerous ampullary canals ; the 
openings of some of which are with difficulty distinguished from the openings of the 
tubules. 



70 PROFESSOR J. C. EWART ON THE 

The infra-orbital canal has a simpler course than in most Selachians, and the absence 
of the suborbital loop, found, for example, in Acanthias, is especially noteworthy. 

Allis considers the infra-orbital canal of Amia as the main canal of the cranial 
system. He describes it as being " directly continuous with the lateral canal." i.e., as 
extruding in Amia to the posterior boundary of the cranium (21, fig. 3, PI. II.) — some 
distance beyond the " supra-temporal cross commissure" (lc., fig. 3). 

The infra-orbital canal of Allis is thus something more than the canal of the buccal 
nerve, for it receives branches from the glossopharyngeal and vagus nerves ; and this 
being the case, it must presumably have originated from parts of three branchial sense 
organs. It seems to me most desirable in dealing with the canals, to be guided as far as 
possible by their innervation. Hitherto the canal of the lateral line has been usually 
described as terminating at the anterior end of the trunk, i.e., as not extending into the 
head region ; but, seeing that the lateral canal is supplied throughout by a cranial nerve, 
I fail to see why it may not be considered as extending into the head region. If it is 
right to consider the supra-orbital canal as co-extensive with branches of the ophthalmicus 
superficialis nerve, and the hyomandibular with branches of the hyomandibular nerve, in 
other words, to consider the whole of the canals, or portions of canals, developed in 
connection with any given nerve as forming one system, it is only logical to look upon 
the whole of the canal or canals innervated by the lateralis nerve as forming one system, 
and to consider the infra-orbital canal as coming to an end at the point where it ceases 
to be supplied by the buccal nerve. Following this plan in the case of Amia, I would 
describe the infra-orbital canal as beginning at the upper end of the hyomandibular canal 
(HM. 1 , fig. 3), and extending forwards and then downwards under the eyeball, after 
communicating with the supra-orbital. If, as seems probable, the superficial ophthalmic 
and buccal nerves and their ganglia have resulted from the splitting of a single nerve, it 
might be more accurate, in the case of Amia, to consider the canal between the upper 
end of the hyomandibular canal and the point at which the supra- and infra-orbital canals 
separate from each other as a special (say otic) portion (ot., fig. 3) — formed from an 
unsplit part of an embryonic sense organ — more especially as in Amia it is supplied by a 
nerve (ot.n., fig. 3) which springs, according to Allis, directly from the facial ganglion. 

The short portion (T., fig. 3) in Amia, between the upper end of the hyomandibular 
(operculo-mandibular of Allis) and the supra-temporal cross commissure (lc, fig. 3), 1 
would describe as the temporal canal or canal of the glossopharyngeal nerve ; and the 
whole of the canal behind this, on to the end of the trunk, including the supra-temporal 
cross commissure, I would describe as the lateral canal — the canal of the lateralis nerve. 
If in the ancestral forms there was but a single cranial canal, as there is now only a 
single canal in the trunk, it is possible that the single ancestral cranial canal is now 
represented by the infra-orbital canal. This is a point, however, that may be made clear 
when the development of these canals is worked out. Assuming that the infra-orbital 
is the main canal of the head, as the lateral is the main canal of the trunk, the supra- 
orbital would require to be looked upon as a dorsal offshoot from the infra-orbital ; and 



SENSORY CANALS OF L^MARGUS. 71 

the hyomandibular, either as a ventral offshoot or as an independent canal, developed 
from a branchial sense organ immediately behind the one in connection with which the 
infra-orbital canal originated. 

The supra-orbital offshoot may have been developed as the eye increased in size ; 
while the hyomandibular offshoot or canal is in all probability correlated to the mandible, 
and, when present, the operculum. It is, however, extremely probable that from the 
first the main canal of the head forked on reaching the orbit, and thus formed supra- and 
infra-orbital canals. 

The accessory or proximal portion of the infra-orbital canal in Lsemargus may be 
known as the otic part (ot., fig. 1). Though continuous with the anterior part of the 
lateral canal, it is not continuous with the infra-orbital. It may be considered as repre- 
senting that part of the canal system in Amia containing the sense organs numbered 15 
and 16 (fig. 3), which are supplied by the otic branch of the facial nerve. 

The otic canal in the specimen of Lsemargus under consideration is 2*5 cm. in length. 
It begins 1 cm. behind and slightly further from the middle line than the common 
terminal pore of the supra- and infra-orbital canals. It then bends outwards and back- 
wards, and on the way gradually sinks to a distance of 4 mm. from the surface, and 
becomes continuous with the cranial portion of the lateral canal.* The canal is penetrated 
by four branches of the otic nerve, and it opens to the surface by four tubules, the anterior 
tubule having a length of 3 '5 mm., the others increasing in length from before back- 
wards — the fourth measuring 7 mm. — the increase being partly due to the deeper position 
of the canal, and partly to the posterior tubules running obliquely outwards through the 
skin. 

The part described as the otic canal I expected at first to find supplied by a dorsal 
branch of the glossopharyngeal nerve — a nerve which, even in Amia, takes part in 
innervating the lateral sense organs. Hitherto, however, I have failed to trace any 
branches from the glossopharyngeal to either sensory or ampullary canals in Lsemargus. 
It is, however, possible that the most anterior portion of the lateral canal — the part 
immediately continuous with the otic — is supplied by fibres which spring from the glosso- 
pharyngeal nerve before it leaves the cranial cavity. 

Innervation of the Infra-orbital Canal. — The otic portion is supplied by fibres which 
leave the buccal nerve immediately after it separates from the superficial ophthalmic. 
As the buccal passes outwards and forwards to run under the eyeball it gives off branches 
for the first portion of the infra-orbital canal proper. It then divides into two main 
branches, the inner of which supplies the sense organs of that part of the canal which 
runs inwards and forwards under the rostrum, while the outer division supplies the sense 
organs of the intermediate part of the canal. 

3. The Hyomandibular Canal. — This canal (HM., fig. 1) which, as already 
explained, is only partially represented in Lsemargus, consists of a canal about 10 cm. in 
length, which runs backwards and outwards from the infra-orbital canal. This part of 

* This is supposing the glossopharyngeal nerve sends no branches to the sense organs. 



72 PROFESSOR J. C. EWART ON THE 

the hyomandibular corresponds to the angular and jugular canals [ang. and j., fig. A) of 
Garman. It lies immediately under the skin, and gradually diminishes in size from 
before backwards. It receives eighteen branches from the hyomandibular nerve, and 
communicates with the surface by eighteen tubules and a small terminal pore. The 
majority of the tubules run directly outwards, and are consequently extremely short ; 
but a few which run obliquely inwards are slightly longer. 

As already mentioned, the hyomandibular (operculo-mandibular) is more extensive in 
Amia than in Lsemargus. Beginning on a level with the infra-orbital canal (HM. 1 , 
fig. 3), it courses downwards and forwards to reach and extend along the entire length 
of the mandible (HM. 2 , fig. 3). In the case of Chlamydoselachus, the lower or mandi- 
bular portion (oral of Garman) is complete ; and there are, in addition, to use Garman's 
terms, angular (ang.), jugular (j.), spiracular (sp.), and gular (g.) portions (fig. 4). 

In some sharks, the mandibulars are represented by a continuous commissural canal, 
in others by two short isolated canals ; but in the skate, as will be described in a future 
paper, each hyomandibular gives off a long ventral loop, the outer limb of which reaches 
the dorsal surface, and runs backwards to terminate in an offshoot from the lateral 
canal. 

Innervation of the Hyomandibular Canal. — The sense organs of the hyomandibular 
canal in Lsemargus are supplied by branches of the hyomandibular nerve, which leave the 
main trunk in the region of the hyoid group of ampullae. 

4. The Canal of the Lateral Line. — This canal may be said to consist of three 
portions : — (1) the trunk portion, which, beginning on a level with the spiracle, extends 
backwards along the side of the body to end on a level with the terminal portion of the 
vertebral column; (2) a transverse portion (lc., fig. 1), which runs inwards behind the 
auditory pore to form with a corresponding portion from the canal of the opposite side 
the temporal commissure ; and (3) a short pre-oommissural part (lp., fig. 1) which 
runs forwards to join the otie portion of the infra-orbital. All the three parts (with the 
possible exception of the portion immediately behind the otic) are supplied by the nervus 
lateralis. The anterior or pre-commissural portion measured 1*25 cm. in length. It 
receives branches from the most anterior fibres of the lateralis nerve, and opens to the 
exterior by five tubules which curve outwards and backwards. This portion of the lateral 
corresponds to a part of the occipital canal of Garman (oc., fig. A). Further investiga- 
tions may show that one or more of its sense organs are, as in Amia, supplied by the 
glossopharyngeal nerve. The commissure (aural canals of Garman, au., fig. B) connect- 
ing the two main lateral canals was 8 cm. in length. Eunning across from 3 to 4 mm. 
beneath the surface and about 6 mm. behind the auditory pores, it opens through the 
skin by sixteen short, delicate tubules, and its floor is perforated by sixteen pores for 
branches of the most anterior fasciculus of the lateralis nerve. It may be mentioned that 
in Chlamydoselachus, the temporal commissure lies in front of the auditory pores and 
has no tubules (fig. 5). This difference in the relation of the canal to the auditory pores 
is more apparent than real ; for even in Chlamydoselachus the commissure lies behind 



SENSORY CANALS OF L^EMARGUS. 73 

the vertical parts of the Fallopian canals ; and its apparent altered position is due to 
these canals being continued some distance backwards under the skin, before opening to 
the exterior. In Heptanchus, the aural portions of the lateral canals do not unite to 
form a commissure ; while in Acanthias, the commissure, instead of running right across, 
bends forwards a short distance between the auditory pores^ 

The main part of the lateral canal (L., fig. 1) begins on a level with the spiracle (sp., 
fig. 1), and runs backwards in a nearly straight line until on a level with the posterior 
margin of the lower lobe of the caudal fin, when it bends downwards to reach the lower 
edge of the caudal muscles. It then runs obliquely upwards along the edge of the 
muscles to terminate on a level with the last seo-ment of the vertebral column. Through- 
out its whole extent, the lateral canal is tubular, and thus differs from the arrangement in 
Chlamydoselachus and Heptanchus, in which the lateral eanal is represented throughout 
the whole, or nearly the whole, length by a groove or furrow. Along its entire length, 
the lateral canal lies immediately beneath the skin, or partly embedded in its substance. 
The first part of the lateral canal behind the commissure resembles the supra- and infra- 
orbital canals ; it has nearly the same form and diameter as the part of the canal in front 
of the commissure. But about 8 cm. beyond the commissure, the canal is reduced in size 
(in the greater part of the trunk to, on an average, 2*5 mm., and in the caudal region to 
about 2 mm. in breadth) ; and throughout it presents a somewhat flattened appearance. 
The tubules are more slender in the trunk than in the head, and the apertures are slightly 
smaller, and consequently less evident. The anterior tubules, owing to their running 
obliquely outwards through the skin, are nearly one centimetre in length ; the remainder 
are slightly shorter — the length, in all cases, depending chiefly on the angle at which they 
traverse the skin. As in the cranial canals, the tubules are all quite simple. 

Innervation of the Lateral Canal. — In the embryo Selachian, five sense organs are 
said to lie above the five branchial clefts ; one above the cleft of the glossopharyngeal 
nerve, and four above the clefts of the four branchial divisions of the vagus. Hence, in 
a typical condition, we might expect to find, extending from the auditory region back- 
wards, a canal innervated by five dorsal (supra-branchial) branches ; one branch from 
the glossopharyngeal, and four branches from the vagus. If, however, we consider the 
condition in the adult, we find, e.g., in the case of Amia, that while the glossopharyngeal 
nerve supplies one of the cranial sense organs, all the other (post-auditory) sense organs 
are innervated by the nervus lateralis of the vagus complex. In Lsemargus, the 
glossopharyngeal nerve has the typical branches, and a well-marked ganglion; but I 
have failed to trace any of its fibres to the sense organs of the lateral canal. The four 
branchial divisions of the vagus are all well developed ; they have in connection with 
them an extremely large ganglion ; nevertheless, they take no part, as far as I can dis- 
cover, in innervating any portion of the lateral canal. 

In all the specimens of Lsemargus examined, the lateralis division of the vagus has: 
been the only nerve found passing to the lateral canal— the commissural, and pre-com-; 
missural portions included. .'..„.. : ■ . . :l 



74 PROFESSOR J. C. EWART ON THE 

It might be asserted that in the case of Lsemargus, the sensory fibres of the five 
dorsal branches of the branchial divisions of the vagus have united together to form the 
lateralis nerve. A careful examination, however, of the lateralis seems to point to a 
different conclusion. The fibres which form the lateralis nerve spring from the side of 
the medulla nearly in a line with the middle roots of the facial nerve ; and the anterior 
fibres lie in front of, and on a higher level than, the roots of the glossopharyngeus. 

Further, although the lateralis accompanies the other divisions of the vagus through 
the long vagus canal behind the auditory capsule, it is only intimately related to the 
nerve of the first vagus cleft. In connection with the lateralis and the first division of 
the vagus (vagus I.) there is a ganglionic swelling crowded with large ganglionic cells. 
Taking these and other facts into consideration, it may be inferred that the lateral canal 
has been mainly developed from a sense organ on a level with the first vagus cleft, and 
in relation with a special group of sensory fibres (similar to those of the facial which 
innervate the three cranial cauals already described), which afterwards gave rise to the 
lateralis nerve. It may be further inferred that by growing in different directions, this 
embryonic sense organ has given rise to the pre-commissural, commissural, and trunk 
portions of the lateral canal, with or without involving the branchial sense organs lying 
above the second, third, and fourth vagus clefts. 



IV. The Dorsal Branches of the Cranial Nerves. 

Having succeeded in making out the innervation of the cranial canals in an Elasmo- 
branch, in showing that the canals instead of being mostly supplied by the trigeminal, 
as has been hitherto supposed, are intimately related to certain well-marked divisions or 
branches of the facial and vagus nerves ; and having in previous papers dealt with the 
cranial nerves of Lsemargus, Raia, and Torpedo, it is now possible to construct a plan 
indicating the arrangement of the dorsal branches in an adult Selachian. 

Leaving out of consideration the olfactory and optic nerves, the first nerve with a 
dorsal branch is the ophthalmicus profundus (o.n., fig. 2). Notwithstanding the fact 
that this nerve has a distinct root in embryo Elasmobranchs, that it sometimes remains 
separate from the trigeminal in the adult, and that in Laemargus, Raia, Torpedo, and 
others, it has a large ganglion lying sometimes a considerable distance in front of the 
Gasserian ganglion, notwithstanding all these facts, this nerve has sometimes been 
considered a part of the trigeminal, sometimes as belonging to the oculo-motor, or as 
" a communicating nerve between the third and fifth" (36, p. 153). 

A discussion of the views held as to the oculo-motor and profundus nerves would be 
out of place in this paper. It is, however, desirable to say a word as to the composition 
of a dorsal branch. In the case of the dorsal branch of a typical spinal nerve, the fibres 
seem to be entirely distributed to the skin, and hence may be spoken of as somatic 
sensory fibres. In the case of a typical cranial nerve, on the other hand, the dorsal 
branch not only contains ordinary sensory fibres for the skin, but also special (in at least 



SENSORY CANALS OF L^EMARGUS. 75 

a physiological sense) sensory fibres for the lateral sense organs. These fibres may be 
known as special somatic sensory fibres. 

In order to distinguish between these two kinds of fibres, those innervating the sense 
organs might be known as the supra-branchial fibres of the dorsal branch. This would 
admit of the term dorsal, so long in use, being retained in fishes and also in the higher 
vertebrates in which the lateral sense organs, with some possible exceptions, and the 
nerve fibres (supra-branchial) supplying them, have completely disappeared. Seeing 
that not one of the many hundreds of sense organs in the skin of Selachians has been 
found in the skin of adult higher vertebrates, we must expect in studying the dorsal 
branches of the cranial nerves, even in fishes, some of the supra-branchial fibres, either 
in process of degenerating, or entirely absent. 

In the case of the ophthalmicus profundus in Lsemargus, there are no lateral sense 
organs (neither nerve hillocks, ampullae, nor pit organs) supplied by its dorsal branch, 
i.e., what I have designated the supra-branchial fibres of the dorsal branch are either 
absent altogether or have changed their function, and are now playing the part of 
ordinary sensory somatic fibres. That they have degenerated (supposing they once 
existed) and not changed their connections, may be inferred from the fact that when 
the supra-orbital sensory canal disappears, its nerve, the superficial ophthalmic of the 
facial, also disappears. That there is a supra-branchial sense organ in connection with 
the ganglion of the profundus in the embryo, seems to have been placed beyond doubt, 
but it has not yet been shown that the embryonic sense organ in connection with the 
profundus either develops into canals or pit organs. 

What then is the distribution of the dorsal branch of the profundus ? The dorsal branch 
(o.n., fig. 2), on leaving the large profundus ganglion (o.n.g., fig. 2) passes over the 
eyeball under the rectus suj)erior, rectus internus, and obliquus superior muscles, and 
eventually reaches the anterior part of the snout, where it terminates in the skin. The 
profundus, which has a similar distribution in Eaia and in Amia, also gives off several 
branches which enter the eyeball. Some of these branches (long ciliary) arise from the 
dorsal branch as it passes through the orbit (lc, fig. 2), others spring from the ganglion, 
and either pass directly to the eyeball, or unite with a branch of the deep division of 
the oculo-motor, having a similar destination. The ciliary ganglion (e.g., fig. 2) lies at 
the junction of the profundus and oculo-motor fibres. Large ganglionic cells sometimes 
extend a considerable distance along the dorsal branch, and ganglionic cells extend 
from the profundus ganglion to form the ciliary ganglion at the junction of the deep 
branch of the profundus (lr., fig. 2) with a branch (sr., fig. 2) from the oculo-motor (3). 

The second nerve having a dorsal branch is the trigeminal (Tr., fig. 2) ; the dorsal 
branch is the ophthalmicus superficialis trigemini. In sharks and rays this nerve sup- 
plies the eyelids, and the skin over the anterior part of the cranium, but it also sends 
fibres into the snout. More or less distinct in sharks, the superficial ophthalmic of the 
trigeminal in rays consists of very few fibres which, on leaving the trigeminal, at once 
more or less completely unite with the superficial ophthalmic of the facial. 

VOL. XXXVII. PART I. (NO. 5). N 



76 PROFESSOR J. C. EWART ON THE 

The dorsal branch of the trigeminal, like the profundus, neither innervates sensory 
nor ampullary canals. It may, however, supply some of the taste-buds found in the 
roof of the mouth of certain fishes. If these taste-buds are modified lateral sense organs, 
the nerves supplying them are likely to be made up of supra-branchial fibres. 

In Amia it has a similar distribution, but while not connected with canals or pit 
organs, it supplies a number of surface sense organs, and anteriorly completely fuses with 
the ophthalmicus profundus. 

While there is no doubt as to the nature of the first two dorsal branches, it is difficult 
to settle whether the third dorsal branch is represented by one or two nerves — whether 
the superficial ophthalmic and buccal divisions of the facial together represent a single 
dorsal branch. This question has been supposed to depend on a still larger question, 
viz., whether, as suggested by Dohrn (34), there is a hyomandibular segment behind the 
mouth, and in front of the hyoid. If there are two segments — a hyomandibular and a 
hyoid — between the mouth and the auditory region, we should expect to find two dorsal 
nerves. In sharks there are undoubtedly two large nerves, each with a large ganglion, 
extending forwards one above and one below the eyeball ; but these two nerves may 
have resulted from the splitting of a single dorsal branch. That this is the case, may be 
inferred from the fact that the sensory thickening, which in the embryo lies above 
the hyoid arch, bifurcates and grows forwards over the face. The superficial and 
ophthalmic branches of the facial, and their related canals (supra- and infra-orbital), are de- 
veloped in connection with the two forward growths from this sense organ above the hyoid. 

The superficial ophthalmic of the facial {s.o.f., fig. 2) is the first nerve that innervates 
lateral sense organs. Unlike the profundus and the ophthalmic branch of the trigeminus, 
it seems to be entirely made up of supra-branchial fibres, i.e., of special sensory somatic 
fibres. 

Having left the buccal nerve (6k, fig. 2), the facial ophthalmic expands to form a 
ganglion, and then passes forwards above the contents of the orbit, following more or 
less closely the supra-orbital canal, all the sense organs of which it supplies. The rest 
of its fibres reach the superficial ophthalmic group of ampullae (S.O.A., fig. 2). In Amia, 
this nerve supplies a line of pit organs as well as the supra-orbital canal (S.O., fig. 3). 

The buccal nerve (bu., fig. 2) is at first inseparably connected with the superficial 
ophthalmic of the facial. In some cases (e.g., Laemargus) it leaves the ophthalmic on the 
proximal side of the ganglion ; while in others (e.g., Amia) the two ganglia are united 
at their proximal ends. In other words, the fusion is more complete in some cases than 
in others ; or, according to the other and more likely view, the splitting is less extensive 
in Amia than in Lsemargus. The buccal, which like the ophthalmic of the facial, seems 
to consist entirely of supra-branchial fibres, having left the ophthalmic, at once passes 
outwards and downwards under the orbit, and divides into two main branches (6k 1 , bu. 2 ), 
which lie in intimate relation with the maxillary and mandibular divisions of the 
trigeminal. The buccal supplies (l) the sense organs of the infra-orbital canal, and (2) 
the inner and outer buccal groups of ampullae. 



SENSORY CANALS OF L^MARGUS. 77 

It seems at first sight remarkable that the sense organs of the snout in Selachians — 
the sensory canals and ampullae — are not supplied as has hitherto been supposed by the 
trigeminal, but by the facial, a nerve which, without doubt, belongs to a posterior 
segment. It is, however, no more remarkable than the innervation of the entire length 
of the lateral canal by the lateralis division of the vagus, and may be accounted for by 
the two portions of the branchial sense organ, that in the embryo lies above the hyoid 
cleft, growing forwards over the head (carrying their nerves with them) in very much 
the same way as the lateral canal grows backwards along the trunk. 

Although I have not thought it necessary to discuss the question as to the segmental 
value of the ophthalmic and buccal divisions of the facial, I may state that, with Van 
Wijhe (35), I regard them as together representing a single dorsal branch, i.e., that 
they have both been developed in connection with a single branchial sense organ. 

The next dorsal nerve, the hyomandibular (hm., fig. 2), also belongs to the facial. 
It is an extremely large nerve in many Selachians, more especially in the skates, and, 
unlike the dorsal nerves already considered, it runs outwards almost at right angles to 
the long axis of the head. While the superficial and buccal branches of the facial have 
in all probability been formed by the splitting of a single dorsal branch, much might be 
said in favour of considering the large bundle of sensory fibres that proceeds outwards 
behind the spiracle, as representing an independent dorsal branch. If the sensory fibres 
of the hyomandibular nerve represent one dorsal branch, and the ophthalmic and buccal 
branches of the facial together represent a second dorsal branch, there is no escape from 
the conclusion that there are two nerves between the trigeminal and auditory — a con- 
clusion which supports strongly Dohrn's contention that there is a hyomandibular as 
well as a hyoid segment. On the other hand, it is possible that all the three dorsal 
nerves, viz., ophthalmic, buccal, and hyomandibular, and their respective canals and 
ganglia, have been formed in connection with a single branchial sense organ which grew 
outwards behind the spiracle, as well as forwards above and below the orbit. 

The large nerve which supplies the hyoid and mandibular* groups of ampullae, 
and the hyomandibular sensory canal, has until recently been looked upon as a branch 
of the trigeminal, and strangely enough has not found a place in the various schemes 
prepared with a view to illustrating the branchial, sense organs, and the segmental 
arrangement of the cranial nerves. The hyomandibular nerve, made up entirely of 
supra-branchial fibres, extends outwards behind the spiracle towards the great hyoid 
group of ampullae (H.A., fig. 2). A large number of the fibres abruptly end in the 
ampullae, others pass in front of or through the ampullary eapsule and end in the sense 
organs of the hyomandibular canal (HM., fig. 2), and the mandibular group of ampullae 
(M.A., fig. 2). A nerve (f.a., fig. 2) corresponding to the facial of the higher vertebrates 
lies in contact with the hyomandibular. It contains no supra-branchial fibres, but a branch 
which runs backwards to the first branchial cleft may include some fibres for the skin. 

* The mandibular group of ampullae, which is easily found in the skate, has not hitherto been referred to by any 
writers on the lateral sense organs. 



78 PROFESSOR J. C. EWART ON THE 

Leaving out of consideration the auditory nerve (Aw., fig. 2), the next dorsal branch 
springs from the glossopharyngeus. This nerve I have traced to the skin over the 
auditory region, but though I have not yet succeeded in tracing it to any of the sense 
organs of sharks, I am inclined to believe that, as shown in the scheme (gl., fig. 2), it 
innervates one or more of the sense organs immediately in front of the most anterior 
organs supplied by the lateralis nerve, and also the auditory group of follicles (pit 
organs) found in the skate. Allis has shown that it supplies one sense organ, and a 
long transverse row of pit organs in Amia (gl., fig. 3). Hence its direct relation to sense 
organs has been sufficiently established in at least one group of fishes. Pit, or at least 
pit-like, organs are sometimes found in the mouth and pharynx of fishes, almost identical 
with those in the skin. Sometimes they lie in the sides of the branchial clefts, and 
they are even said to extend into the oesophagus. The pit-like organs in the mouth are 
usually described as taste-buds. In the mammal they are said to be innervated by the 
glossopharyngeal nerve, and it has been suggested by Beard and others that they are 
modified lateral sense organs that have reached the back of the tongue, palate. &c. 
through one or more branchial clefts. If the taste-buds are altered lateral sense organs 
innervated by the glossopharyngeus, the fibres reaching them will belong to the dorsal 
branch. It does not, however, follow that because the taste-buds are innervated by the 
glossopharyngeal they are altered lateral sense organs, for the nerves reaching them may 
spring from the pharyngeal branch, and consist of special sensory splanchnic fibres. 

The next dorsal branch (In., fig. 2) arises from the great vagus complex. It is not 
yet possible to speak definitely as to the dorsal branches of the vagus for the reason that 
it has not yet been determined how many of the branchial sense organs lying above the 
branchial clefts of the vagus take part in the formation of the lateral canal. According to 
Beard (27), " the ' lateral line ' has arisen solely by the extension and multiplication of 
the primitive branchial sense organs of the vagus." He observes they are " connected in 
development, being formed from one continuous sensory rudiment, and as they form one 
physiological whole, we could expect a connection in the adult." Beard describes first 
what he terms vagus I., i.e., the nerve of the first vagus cleft. It appears that from the 
long sensory thickening above the vagus clefts, to which the broad band representing all 
the vagus nerves grows out, there is soon slightly separated the anterior portion which 
gives rise to the ganglion of vagus I., and later, to part of the supra-temporal branchial 
sense organs. The rest of the sensory thickening is described as growing backwards along 
the lateral surface of the trunk, i.e., the sensory cells, " which anteriorly give rise to the 
compound vagus ganglion (v.g. 2, 3, and 4), repeatedly and rapidly divide," and thus 
give rise to the "lateral line." Again, it is stated, "each of the elementary nerves 
making up the vagus compound, viz., v.g. 2 and 3, and the intestinal branch, v.g. 4 and 5, 
takes part in the formation of the so-called ' lateral line.' * In other words, " the lateral 
line is made up of supra-branchial nerves of at least four segmental nerves, probably of 
more than four, viz., vagus 2, 3, 4, and 5." It is further stated, that there is only one supra- 
branchial branch — the lateral nerve — for all the elements of the vagus except the first (27). 



SENSORY CANALS OF L^MARGUS. 79 

From these statements I infer that while the supra-branchial branch of vagus I. (the 
nerve of the first vagus cleft) supplies thesupra-temporal sense organs, the united supra- 
branchial branches of vagus II. , III., IV., and V. form the lateralis nerve and innervate 
the sense organs of the lateral canal of the trunk, or, more accurately, the sense organs of 
the lateral canal not supplied by vagus I. 

In the case of the facial the majority of the sensory fibres for the sensory canals, 
i.e., the fibres of which the superficial ophthalmic, buccal, and the greater part of the 
hyomandibular nerves are largely composed, escape at a comparatively high level from 
the side of the medulla. From the side of the medulla in front of and on a higher level 
than the root of the glossopharyngeal and the rootlets which unite to form the chief 
portion of the vagus, there escape a number of fibres which unite to form the nerve 
(lateralis) which supplies the entire length of the lateral canal, the temporal commissure 
included. In Lsemargus this nerve lies in intimate relation with the first division of 
the vagus (vagus I.). In the skate, it is from the first a distinct nerve, with an inde- 
pendent ganglion (l.g., fig. 2), but it may receive fibres from the branchial divisions of the 
vagus. In Lsemargus the three posterior branchial divisions of the vagus, together with 
the intestinal branch, are inseparably united, and in connection with one long ganglion, 
but they send no distinct branches to the lateralis nerve. In Eaia, the three posterior 
branchial branches of the vagus, and the intestinal branch, are in contact with each 
other, but not blended, and each, like vagus I., has a distinct ganglion (I.-V., fig. 2), but, 
as in Lsemargus, they send at the most very slender branches to the lateralis nerve. The 
condition in the adult thus seems to indicate that the lateral canal as above described 
has mainly arisen from the branchial sense organ above the first vagus cleft, and that the 
epidermic thickenings above the second, third, and fourth vagus clefts, while probably 
assisting in forming a long ganglion (Lsemargus), or four separate ganglia (Raia), have 
taken little or no part in forming the "lateral line." The lateralis nerve behind the 
first branchial cleft consists entirely of special sensory somatic fibres ; in front, it seems 
to be accompanied by a few ordinary sensory fibres which reach the skin. 

If figure 2 is compared with the schemes previously published, it will be found to 
differ in several important points. It contains not only the dorsal but also the more 
important branchial and visceral branches, and in addition to the sensory canals, the 
various groups of ampullae, and also the follicles or pit organs. 

It is not intended to represent the arrangement in any given Elasmobranch, but 
rather to indicate the position, innervation, &c, of the lateral sense organs in a Selachian 
having these structures well developed. In the schemes hitherto constructed, the relation 
of the profundus nerve to the ciliary ganglion, and to the oculo-motor nerve, is not 
shown, and it is taken for granted that the profundus supplies a group of sense organs. 
This scheme represents (1) the dorsal branch of the profundus (o.n.) proceeding to the tip 
of the snout without supplying either sensory or ampullary canals ; (2) the long ciliary 
nerves (I.e.) passing to the eyeball ; and (3) the offshoot (l.r.) to the ciliary ganglion (e.g.); 
this offshoot may, perhaps, be looked upon as a visceral branch. 



80 PROFESSOR J. C. EWART ON THE 

The trigeminal (tr.) agrees with the trigeminal of other schemes ; but as in the case of 
the profundus, it is not represented as taking any part in innervating lateral sense 
organs. It gives off a dorsal branch (s.o.L), and sends one branch (m.x.) in front of, and 
a second (m.d.) behind the mouth. 

There is, however, a marked difference between the facial of this and other schemes. 
The facial was considered by Marshall (36) as a simple and typical nerve, and it has been 
represented as possessing a single root, a single root ganglion, and as breaking up into 
the three typical branches, i.e., dorsal, pre- and post-branchial branches — the dorsal branch 
forking as it proceeds forwards. In my scheme the facial is represented as arising by 
five roots and possessing three large dorsal branches, each with a ganglion. One of the 
roots (f.a.) lies immediately in front of the auditory nerve. This root, which has an 
independent ganglion, and represents the facial of the higher vertebrates, breaks up into 
four branches — a dorsal (d.f.), which passes backwards towards the first branchial cleft ; 
a small pre-branchial (p.s.) in front of the spiracle ; a larger post-branchial (p.b.), which 
passes behind the spiracle round the hyomandibular cartilage to proceed to the mucous 
membrane of the mouth within the hyoid arch; and a pharyngeal (p.l.) which supplies 
the roof of the mouth. As the post-branchial branch bends forwards, it sends a few 
fibres to the muscles in the region of the hyoid cartilage and the jaw arches. These 
motor branches reach a large size in the torpedo, and they represent the main portion of 
the facial of higher vertebrates. 

Two of the dorsal branches — the superficial ophthalmic (s.o.f.) and buccal (bu.) — 
result from the splitting of an originally simple branchial sense organ. The superficial 
ophthalmic passes above the eyeball to supply the supra-orbital canal, and the superficial 
ophthalmic group of ampullae. The buccal passes below the eyeball and supplies the 
infra-orbital canal and the inner and outer buccal groups of ampullae. The third dorsal 
branch — the segmental value of which is not yet known — runs outwards behind the 
spiracle and supplies the hyomandibular canal and the hyoid and mandibular groups 
of ampullae. This hyomandibular nerve has not hitherto found its way into any of the 
schemes intended to show the general arrangement and distribution of the cranial nerves. 

The glossopharyngeal in my scheme agrees in its arrangement with that of other 
schemes. It is represented as giving off the four typical branches. The dorsal one I 
have represented as supplying a short part of the great lateral canal as well as a row of 
pit organs ; but I ought to mention that though this is the distribution of the glosso- 
pharyngeal in Amia (30), it has not yet been traced to sense organs in Selachians. 

The vagus complex, as shown in my scheme, differs very considerably from the vagus 
of other writers. I have found it far more simple and primitive than I expected. The 
usual plan has been to represent the vagus as made up of (1) one separate nerve with 
a ganglion for the first vagus cleft, and (2) of a compound nerve with one large ganglion 
made up of fibres for the three or four remaining clefts. The first nerve (vagus I.) has 
been described as having a dorsal branch for the supra-temporal commissure, while the 
nerve for the lateral line of the trunk has been described as springing from the large 



SENSOR? CANALS OF L^EMAEGUS. 81 

compound nerve, and made up of four sets of dorsal fibres — the dorsal branches of vagus 
II. i III., IV., and V. In my scheme, which represents the arrangement in Raia and 
Lamna, the lateralis nerve is represented as springing by a special set of fibres on a 
higher level and partly in front of the glossopharyngeal, and it supplies not only the 
lateral line (the lateral canal of the trunk), but also the temporal commissure and a 
portion of the great lateral canal in front of the commissure. The lateralis either receives 
from or gives slender branches to the four or five divisions of the vagus as it proceeds 
backwards ; but whether this implies that all the divisions of the vagus have contributed 
to the formation of the lateralis, I am not yet in a position to say. Strangely enough, 
the lateralis has a special and distinct ganglion. 

Vagus I., II., and III., in the case of the skate, are all separate nerves, and each has a 
ganglion, visceral, pre- and post- branchial branches. Vagus IV., which has also the 
usual branches, is intimately connected with the intestinal division, but the ganglia are 
partly or completely separate. In the skate there are thus in connection with the vagus 
six ganglia. The value of these, and especially the origin of the ganglion of the lateralis, 
whether it arises independently or from vagus I., or from all the branchial divisions of the 
vagus, are points well worth further investigation. 

It is worthy of note that all the groups of ampullae — the superficial ophthalmic 
(S.O.A.), inner (I.B.A.) and outer (O.B.A.) buccal, hyoid (H.A.) and mandibular (M.A., 
fig. 2) — are supplied by dorsal branches of the facial, and that the lateralis, in addition 
to supplying the entire length of the lateral canal, innervates (e.g., in Mustelus and 
Raia) a row of pit organs (p.od., fig. 2). 

Concluding Observations. 

Although from a morphological point of view there seems no doubt that the sensory 
canals subserve some important function, it has not yet been discovered by actual 
experiment what this function is. 

Garman (29) thinks that it has been pretty well established that the function of the 
sensory canals is " that of very delicate tactile organs receiving and carrying the slighter 
vibrations of the water, noting changes of density, currents, &c." 

It is now most desirable that experiments should be instituted, under favourable 
conditions, to test the various suggestions made as to the function of both the sensory 
and ampullary canals. In view of further experiments being undertaken, I cannot do 
better, in concluding this paper, than point out some of the more striking modifications 
of the sensory canals found in Elasmobranchs.* 

In the first place, in some of the sharks, as already noted, a furrow takes the place of the 
greater extent of the lateral canal. In Chlamydoselachus, e.g. , the lateral canal, with the 
exception of a small part behind the temporal commissure, is represented by a groove, 
guarded by overlapping scales. In Heptanchus maculatus, the canal opens into a groove 

* For outline figures showing the arrangement of the canals, see Garman (29). 



82 PROFESSOR J. C. EWART ON THE 

on a level with the anterior part of the pectoral fin ; while in Acanthias, the canal is 
closed except for a short distance in the caudal region. In as far as these species have 
furrows, they agree with Chimsera, in which grooves take the place of canals in the head 
as well as in the trunk, but differ from Callorhynchus, which has canals like the skates 
and rays, and the majority of the sharks. The difference, however, between canals and 
furrows is, in most cases, more apparent than real, as the sense organs which lie in the 
furrows are protected by overlapping scales or folds of skin, which practically convert the 
furrows into canals. 

In some sharks, the arrangement of the canals is simpler and the tubules less 
numerous than in others. In Laemargus and Heptanchus, the arrangement of the canals 
is very simple. Their length has not been greatly increased by the formation of loops, 
and the tubules are short and never break up into branches before opening on the 
surface. But in the extremely active thresher shark Alopias, there is a loop on the infra- 
orbital under the eyeball ; and the mandibular part of the hyomandibular is well 
developed and provided with long branching tubules. But Alopias is especially noticeable 
for the remarkable development of the lateral canal and its tubules, which are not only 
extremely abundant, but are of unusual length, and give off numerous branches. 

It is extremely probable that the remarkable development of the tubules in Alopias is 
related to the active pelagic habits of the fish, which in this respect differs strikingly 
from Lgemargus, which, from its being frequently taken in the beam trawl, seems to move 
about in a leisurely manner, near the bottom. 

Further evidence of a relation between the development of the sensory canals and the 
habits of the fish is especially found among the skates and rays (Batoidei). In the 
common skate [Raia batis) the expansion of the pectoral fins has been accompanied with 
a great extension of the hyomandibular canal ; and the appearance of long, dorsal offshoots 
or branches from the lateral canal. 

That there is a relation between the extent of the sensory canals and the size of the 
pectorals is placed beyond doubt by comparing the condition of the canals in the more 
specialised Batoidei with such shark-like forms as Ehinobatis and Pristis. In these, 
although the ventral loop so characteristic of the Batoidei has made its appearance, it is 
very short and narrow, not reaching as far as the first branchial cleft. 

As fully explained in a paper in process of preparation, the hyomandibular in the 
skate has extended backwards external to the branchial region to form a long, wide, 
ventral loop, one end of which passes to the upper surface to form, with a branch from 
the lateral, a long and still wider dorsal loop over the pectoral fin ; while a second branch 
from the lateral extends over the fin behind the loop. 

By these extensions and folds an extremely sensitive apparatus has been arranged 
over the surface of the pectoral fin. Though, in the meantime, it is impossible to 
account for these complex arrangements of the sensory canals, it may be taken for granted 
that they are far from meaningless. 

In the rays there seems to be, as in the sharks, a relation between the development 



SENSORY CANALS OF L^M ARGUS. 83 

of the sensory canals and the habits of the fish. In the sluggish members of the Batoidei, 
the canals are in a more or less vestigial condition ; while in the active forms they are 
amazingly complex. For example, in Narcine hraziliensis, a small inactive torpedo found 
often in brackish water on the east coast of Central America, in the Caribbean Sea, and 
on the coasts of the West Indian Islands, the whole of the ventral canals are absent, and 
the supra-orbital stops short on a level with the nasal capsule ; and while the dorsal loop 
is present, the post-scapular branch is undeveloped. Moreover, the tubules are few in 
number, short and simple, and the number of the sense organs is limited. 

In the torpedoes, a similar state of matters prevails. They are all, apparently, in the 
habit of resting long on the bottom ; and with the possible exception of one or two 
species, they seldom seem to move, save in the most sluggish fashion. As the sluggish 
habits were gradually acquired, the extent of the sensory canal system, it may be pre- 
sumed, has been gradually reduced. The ventral sensory canals having become useless, 
natural selection has made no effort to preserve them, with the result that only vestiges 
are left in the form of small vesicles — the follicles of Savi — one for each of the sense 
organs that persist in connection with the ventral branches of the facial nerve. At the 
same time, the dorsal sensory canals are, compared with the skate, less highly developed ; 
the canals are simpler in their arrangement ; the post-scapulars are entirely absent ; and 
the tubules in most species are simple, short, and few in number. 

If, from the sluggish electric rays, we turn to the active Mylobatidse, e.g., to 
Dicerobatus, the difference in development is most striking ; the area covered by the 
tubules and their numerous branches being far more extensive than in the common 
skate ; the openings of the tubules being especially numerous on the ventral surface, 
and on the dorsal surface near the margins of the pectoral fins, and at each side of the 
middle line of the trunk. The ventral loop, which even in the skate is almost destitute 
of tubules, has in Dicerobatus reached an extraordinary development, and throws 
numerous branching tubules backwards towards the pelvic fin ; and there is a row of 
tubules along the entire length of the anterior border of the pectoral fin. On the dorsal 
surface, the branching tubules from the lateral canal are so numerous that they seem to 
form a network at each side of the middle line — some of them even meet in the middle 
line, and thus form trunk commissures ; and a large number of branching tubules occupy 
the area enclosed by the dorsal pectoral loop. 

Judging from the complexity of the sensory canals, and especially from the 
abundance of the tubules — the feelers of the canals — which they throw out in all 
directions, it may be concluded that whatever their function, they are of the utmost 
importance. 

It may be presumed that they take up and transmit various kinds of impressions 
other than those which are taken cognisance of by the sense organs of the auditory 
apparatus. Whether they enable the fish the better to obtain its food, or the better to 
escape from its enemies, or both, remains to be made out. In comparing Dicerobatus 
with the skate (Rata batis) and the torpedo (T. marmorata), one is especially struck with 

VOL. XXXVII. PART I. (NO. 5). 



84 PROFESSOR J. C. EWART ON THE 

the difference in the condition of the sensory canals of the ventral surface. In the 
torpedo the ventral loop is entirely absent, and there are only a few follicles under the 
snout, representing the anterior canals. In the skate, the ventral loop and the various 
ventral portions of the cranial canals are well developed, but the tubules are extremely 
few in number — the long loop only possessing nine in all. In Dicerobatus, as pointed 
out above, the ventral loop and its tubules have reached a state of great elaboration. 
These differences might very well be accounted for by the differences in the mode of life 
of the three forms. The torpedo moves about little, and trusts both for its defence and 
its food to its batteries ; and the sensory canals are, as it were, only sufficiently developed 
to enable it to appreciate ordinary disturbances in its immediate vicinity. 

The skate moves about more than the torpedo, but less than Dicerobatus ; but in its 
movements it usually keeps close to the bottom, and apparently it has comparatively few 
enemies. It is far less often captured by other fish than one would naturally suppose ; 
and it seems to have little difficulty in obtaining its food. Hence, though the ventral 
loop is present, it possesses few tubules ; and, though the dorsal canals are well developed, 
the tubules are simple and less numerous than in Dicerobatus. 

As to the habits of Dicerobatus, little is known ; but it undoubtedly differs from both 
the torpedo and the skate. Instead of resting almost constantly on, or merely skimming 
along the bottom, it is in the habit of taking long flights through the water. This prob- 
ably accounts for the great development of the tubules of the ventral loop. Why the 
dorsal tubules are so enormously complex is more difficult to account for ; but their 
development may have some relation to the unprotected condition of the tail, which is 
not only devoid of a spine, but comparatively short and powerless. 

Taking into consideration the marked difference between the sensory canals of the 
sharks and those of the skates and rays, it will be well, before dealing further with the 
sharks, to give an account of the sensory canals in one of the Batoidei — this I hope to do 
in a subsequent communication. 

[For Explanation of Plates see page 102.) 



[Bibliography. 



SENSORY CANALS OF L^MARGUS. 85 



BIBLIOGRAPHY.* 

1. Ewaet, "On the Cranial Nerves of Elasmobranch Fishes," Roy. Soc Proc, vol. xlv., 1889. 

2. Ewart, "The Cranial Nerves of the Torpedo," Roy. Soc. Proc, vol. xlvii., 1890. 

3. Ewart, "On the Development of the Ciliary or Motor Oculi Ganglion," Roy. Soc. Proc, vol. xlvii., 1890. 

4. Stenonis, De Musculis et Glandulis Observationum specimen, &c., Amst., 1664. 

5. Stenonis, Elementorum Myologies specimen, &c, Amst., 1669. 

6. Lorenzini, Osservazioni intorno alle Torpedini, Firenze, 1678; Lond., 1705, Angl. 

7. Monro, The Structure and Physiology of Fishes, 1785. 

8. Jacobson, "Extrait d'un M^moire sur un Organe particulier des Sens dans les Raies et les Squales," Nouv. 

Bull, des Sciences, par la Societe Philomatique de Paris, 1813, vi. p. 332. 

9. St Hilaire, "Sur lAnatomie des Organes electriques," &c, Ann. du Mus., i. p. 392, 1801. 

10. Mayer, Spicilegium Observationum anatomicarum de Organo electrico in Raiis anelectricis, 1843. 

11. Lamballe, Des Appareils electriques des Poissons electriques, 1858. 

12. M'Donnell, "Electric Organs of the Skate," Nat. Hist. Review, p. 59. 

13. De Blainville, Principes d'Anatomie comparee, 1822, I. 

14. Robin, Bull. Soc Philomatique, 1846 ; Ann. Sc Nat. (3 e s<h\), vii. pp. 193-204. 

15. Treviranus, "Ueber die Nerven des flinften Paars als Sinnesnerven," Vermischte Schriften anat. und 

physiol. Inhalts., 1820. 

16. Savi, Atti delta terza Riunione degli Scienziati Italiani in Firenze, 1841; "Etudes anatomiques sur la 

Torpille," 1884, in Matheucci Traite des Phenomenes Flectro-physiologiques des Animaux. 

17. Delle Chiaje, Instituzione di Anatomia comparata, 1836; "Anatomiche Disamine sulle Torpedini," in 

Atti del Reale Instituto d'Incorragiamento alle Scienze Naturdli di Napoli, vi., 1840. 

18. Leydig, "Ueber die Schleimcanale der Knochenfische," 1850, Midler's Archiv Anat. 

19. Leydig, "Ueber Organe eines sechsten Sinnes, 1868, Nova Acta Acad. Caes Leap. Nat. Curios, xxxiv. 93. 

20. Muller, H., Verhandlungen der phys.-med. Gesellschaft zu Wiirzburg, 1851. 

21. Kolliker, "Ueber Savi's Appareil folliculaire nerveux," Verhandl. phys.-med. Gesellschaft zu 

Wiirzburg, 1858. 

22. Max Schultze, Untersuchungen iiber den Ban der Nasenschleimhaut, 1862. 

23. Boll, "Die Lorenzinischen Ampullen der Selachier," 1868, Schultze's Archiv fur mikr. Anat, iv. 

24. Goette, Entwicklungsgeschichte der Unke, 1875. 

25. Semper, Das Urogenitalsystem der Plagiostomen und seine Bedeutung fur das der Uebrigen Wirbelthiere, 

1875. 

26. Balfour, The Development of Elasmobranch Fishes, 1878; Comparative Embryology, 1881. 

27. Beard, " The Branchial Sense Organs and their Associated Ganglia in Ichthyopsida," &c, Quart. Journ. 

Micro. Sc, 1885. 

28. Sappey, Etude sur Appareil mucipare, &c, 1879. 

29. Garman, "On the Lateral Canal System of the Selachia," &c, Bull. Mus. Comp. Zool., vol. xvii. No. 2. 

30. Allis, "The Anatomy and Development of the Lateral Line System in Amia calva," Journal of Mor- 

phology, vol. ii. 

31. Fritsch, " Ueber Bau und Bedeutung der Kanalsysteme unter der Haut der Selachier," Sitzungsberichte 

d. Konigl. Akad. d. Wissensch. zu Berlin, 1884, Halbbd. I. 

32. Fritsch, Die Electrischen Fische, Die Torpedinen, Leipzig, 1890. 

33. Garman, " Chlamydoselachus anguineus, 1885, Bull. Mus. Comp. Zool., xii. 

34. Dohrn, " Studien zur Urgeschichte des Wirbelthierkb'rpers," No. 7, Mittheil a. d. Zool. Stat, zu Neapel, 

vol. vi. part 1. 

35. Van Wijhe, Ueber die Mesodermsegmente u. die Entivicklung der Nerven des Selachierkopfes, Amsterdam, 

1882. 

36. Marshall, "The Segmental Value of the Cranial Nerves," Jour. Anat. and Phys., 1882, p. 164 

* A more complete list of works on the Lateral Sense Organs will be found ia Garman's paper (29). 



PROFESSOR EWART ON THE SENSORY CANALS OF L/tMARGUS. 



Trans Roy. Soc.Edin r 



Yol.XXXYII. 



HM.' 



Ewart del 




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Plate I 



F Hutti, Lift' Edm 1 



PROFESSOR EWART ONTHE SENSORY CANALS OF L/EMARGUS 

ans.Roy.Soc.Edin r Vol XXXVII. 




Plate II 



FHuth.LitW Edm r 



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( 87 ) 



VI. — On the Lateral Sense Organs of Elasmobranchs. II. The Sensory Canals of the 
Common Skate (Eaia batis). By J. C. Ewart, M.D., Eegius Professor of Natural 
History, and J. C. Mitchell, B.Sc, University of Edinburgh. (Plate III.) 

(Read 21st December, 1891.) 

Introductory. 

In the paper on the sensory canals of Lsemargus, communicated to the Royal Society 
in July last, it was pointed out that the arrangement of the sensory canals differed con- 
siderably in the Batoidei from that in Selachoidei, and it was mentioned that the sensory 
canals of the skate would be next described. 

The skate has been selected chiefly because the sensory canals are more typical than 
in the torpedoes and the whip and sting rays. In the torpedoes some of the canals are 
in a vestigial condition ; while in the rays proper they have in most species undergone 
great specialisation. But another reason is, that an account of the development of the 
lateral sense organs in the skate is likely ere long to be published ; and, further, the skate 
will be more easily obtained and kept under observation than the rays, when physiologists 
eventually direct their attention to the lateral sense organs of Elasmobranchs. 

In describing the sensory canals of the skate, an acquaintance with the papers on 
the sensory canals (1) and the cranial nerves (2) of Lsernargus will be taken for granted. 

The General Anatomy and Innervation of the Sensory Canals. 

The lateral sense organs in the skate consist of (1) sensory canals; (2) ampullary 
canals ; and (3) sensory follicles or pit organs. As in Lsernargus, the sensory canals may 
be said to consist of four main canals — viz., (l) a supra-orbital; (2) an infra-orbital; (3) 
a hyomandibular ; and (4) a lateral canal. The ampullary canals radiate from five 
centres, their inner dilated ends giving rise to five groups of ampullae. . One, the most 
posterior (hyoid) group of ampullae, lies at the outer end of the hyomandibular cartilage ; 
a second (the superficial ophthalmic) group lies at the side of the rostrum ; a third (the 
inner buccal) group lies in front of the nasal capsule ; a fourth (the outer buccal) group 
lies in front of the antorbital cartilage ; while the fifth (the mandibular) group lies near 
the outer end of the mandible. The sensory follicles (" spalt-papillen " of Fritsch) consist 
of three rows of shallow pits, one of which lies internal to the canal of the lateral line, a 
second row lies under the orbit, and a third row near the auditory pores. 

In the Lsernargus paper it is pointed out that Stenonis discovered the openings of 
the mucous (ampullary) canals of the skate in 1664, and that both the ampullary and 
sensory canals were discovered some years later (1678) in the torpedo by Lorenzini, who, 

VOL. XXXVII. PART I. (NO. 6). P 



88 PROFESSOR J. C. EWART AND MR J. C. MITCHELL ON THE 

in addition to distinguishing the simple (ampullary) from the branched (sensory) canals, 
noted and described the expansions, now usually known as the ampullae of Lorenzini, 
at the inner ends of the simple canals. Keference was also made to the work of Monro 
secundus, who, in his memoir "On the Structure and Physiology of Fishes" (1785), 
figures, without describing, several of the sensory as well as the more important am- 
pullary canals. The most ambitious paper since the time of Monro, dealing with the 
lateral sense organs of the skate, is one by Sappey (3). Unfortunately, Sappey's account 
of the sensory canals is far from complete, and there is no reference to their innervation. 
The groups of ampullae are described as glands for secreting mucus, and the ampullary 
canals as ducts for conveying the mucus to the surface ; and all the ampullae are said to 
be supplied by the trigeminal nerve. It is difficult to make out which of the skates 
Sappey examined. From the drawings it appears to be R. clavata, but the arrangement 
of the canals in both clavata and batis very decidedly differs from Sappey's figures. 

Three other investigators have considered at some length the lateral sense organs of 
the skate, viz., Merkel, Garman, and Fritsch. Merkel (4) evidently foiled to make out 
the arrangement of the sensory canals in the skate, more especially the hyomandibular 
canal, which is represented in one of his figures as springing from the great lateral canal, 
a condition which does not obtain in any Elasmobranch. 

Garman (5), following Agassiz, studied the sensory canals mainly with a view to 
determining their value in classification. To admit of this, he examined and prepared 
outline figures of the canals of a large number of skates and rays. Necessarily, the 
descriptions are very short, and, as pointed out in the previous paper, there is no attempt 
to consider. the canals either in reference to their development or innervation, with the 
result that a somewhat complex nomenclature has been introduced. Nevertheless, the 
figures and short descriptions of a large number of species cannot but be of service to the 
comparative morphologist as well as to systematists. Again and again we have found 
them most useful. Fritsch (6), in addition to giving a short account of the canal system 
of the torpedo, has described a special form of sense-organ in the skate, to which he has 
given the name of " spalt-papille." Fritsch's spalt-papillse probably correspond to the 
minute pit organs of Amia, Mustelus, and Squatina. 

The four main sensory canals are related to the same nerves as in Laemargus. The 
supra-orbital (S.O. 1 " 5 , figs. 6 and 7, PI. III.), or canal of the ophthalmicus superficialis branch 
of the facial, runs forwards above the eyeball, pierces the snout, and then extends back- 
wards external to the nasal capsule to communicate with the infra-orbital. The infra- 
orbital (I.O. 1-8 , figs. 6 and 7), or canal of the buccal nerve, passes downwards and forwards 
external to the eyeball, and then backwards along the ventral surface to bend inwards 
and forwards after communicating with the supra-orbital and the hyomandibular. The 
hyomandibular (HM 1-0 ., figs. 6 and 7), or canal of the hyomandibular nerve, is far more 
extensive than in any of the sharks, though (as in sharks) the hyoid portion is absent 
and the mandibular portion is incomplete and disconnected. Beginning where the 
infra-orbital bends sharply inwards, it forms a long ventral loop, and then reaching the 



SENSORY CANALS OF THE COMMON SKATE. 89 

dorsal surface it curves backwards, and eventually terminates by communicating with a 
lono- offshoot from the lateral canal. 

The two lateral canals, or canals of the lateralis divisions of the vagus nerves, begin 
on a level with the spiracle (sp., fig. 6), and extend backwards to the tip of the tail, 
giving off branches which unite and form the temporal commissure, and also two long 
(scapular) branches, the anterior of which communicates with the dorsal extension of the 
hyomandibular to form a wide dorsal loop. 

I. The Supra-Orbital Canal. — This canal not only communicates by its proximal end 
with the infra-orbital canal as in Lsemargus, but also with the anterior end of the lateral 
canal, as in Chlamydoselachus, Acanthias, and certain other sharks. Beginning on a 
level with the anterior margin of the spiracle, as shown in figure 6, it first arches inwards 
and then runs forwards parallel to the middle line as far as the nasal capsule ; it then 
inclines inwards as it proceeds to the tip of the snout (S.O. 2 , fig. 6), which it pierces, and 
thus reaches the ventral surface, to run backwards and slightly outwards, as shown in 
figure 7. When some distance from the nasal aperture, it bends forwards and outwards 
to form a close loop (S.O. 4 , fig. 7), and finally runs outwards and backwards in front 
of the nasal capsule, to terminate by opening into the infra-orbital canal (S.O. 5 , fig. 7) 
Notwithstanding the great difference which obtains between the skate and Lsemargus, 
the supra-orbital canal in the skate only really differs from that of Lasmargus in being in 
direct connection with the canal of the lateral line, and in presenting a well-marked loop 
before it unites with the infra-orbital. 

The supra-orbital canal, as above described, includes the cranial, rostral, and subrostral 
canals of Garman (5). The first (cranial) part of the supra-orbital lies immediately under 
the skin, and in some cases occupies a shallow but well-marked groove in the cranial 
cartilage. It has an internal diameter of 0'5 mm., while the entire canal is oval in form, 
measuring about 4 mm. by 2 mm. in thickness. Seven short, slender tubules spring from 
the first part of the canal (t.-t. 7 , fig. 6), and run inwards to open by minute pores about 
1'2 cm. from the middle line. From the next part of the canal, nine slender tubules 
(t.-t. 16 , fig. 6), only one of which is over 3 mm. in length, extend directly outwards, and 
from the part of the canal that lies over the nasal capsule there are seven tubules (t.-t. 23 , 
fig. 6) which run outwards and forwards, the three anterior ones being over 2 cm. in 
length. Passing to the first section of the canal are sixteen nerves, the majority of which 
at once penetrate the canal, but the anterior ones break up and supply the sense organs 
corresponding to the anterior tubules. There are probably altogether twenty-three ter- 
minal branches. 

The part of the supra-orbital canal which runs along the rostrum (rostral canal of 
Garman; S.O^-S.O. 2 , fig. 6) differs from the part just described, and from the cranial 
canals in Lsemargus, in giving off no tubules — in having no direct communication with 
the exterior. It lies about 2 mm. below the skin in the subcutaneous tissue, and has 
throughout the greater part of its length a diameter of 27 mm. It has thus a diameter 
fully five times that of the cranial portion, while the wall is only about 1 mm. in thick- 



90 PROFESSOR J. C. EWART AND MR J. C. MITCHELL ON THE 

ness. As it approaches the tip of the snout it is reduced to 1*4 mm., and this diameter 
it retains for some distance as it extends backwards under the rostrum. The rostral part 
of the canal receives twenty branches from the superficial ophthalmic nerve as it proceeds 
to the tip of the snout. 

The ventral part of the supra-orbital canal (subrostral canal of Garman ; S.O. 3 , fig. 7) 
may be said to consist of three segments — (1) a part lying nearly parallel with the middle 
line ; (2) the loop (S.O. 4 , fig. 7) already mentioned ; and (3) a slightly curved part that runs 
outwards to the infra-orbital (I.O. 4 , fig. 7). The first part, as it runs backwards, increases 
slightly in diameter, and then expands considerably as it turns sharply forwards and out- 
wards to form the loop. As the top of the loop is reached, the canal contracts and again 
expands slightly as it returns to bend backwards and outwards in front of the nasal 
capsule. It lies embedded in the gelatinous tissue of the snout, from 2 to 3 mm. from 
the surface. The first part opens to the exterior by ten extremely short tubules (t.-t. ss , 
fig. 7), the first two being under 2 mm. in length. There are no tubules from the looped 
portion ; there are, however, twelve regularly arranged but short tubules from the terminal 
portion (t.~t. 45 , fig. 7). Passing to the sense organs in the ventral part of the supra-orbital 
canal, forty-five nerves were counted — sixteen to the first part, seventeen to the loop, and 
twelve to the terminal portion. All the nerves to the sense organs of the supra-orbital 
canal spring from the ophthalmicus superficialis of the facial — a nerve which has almost 
universally been described as a branch of the trigeminal, and which is still apt to be con- 
fused with the superficial ophthalmic branch of the trigeminal or with the ophthalmicus 
profundus. 

Innervation. — According to Bfard's scheme, referred to in the Lsemargus paper (1), 
the three ophthalmic nerves — viz., the ophthalmicus profundus, the ophthalmic of the 
trigeminal, and the ophthalmic of the facial — are supra-branchial branches, and each 
should have sense organs in connection with it ; in other words, all three nerves should 
take part in supplying sense organs in the supra-orbital region or in the snout. As to the 
ophthalmicus profundus, which lies in front of the trigeminus proper, we are satisfied that, 
as in Lsemargus and Amia (7), it takes no part in supplying lateral sense organs. The 
superficial ophthalmic branch of the trigeminal so completely blends with the ophthal- 
micus superficialis division of the facial that it is all but impossible to trace its fibres. On 
the other hand, in the Elasmobranchs in which the ophthalmic division of the trigeminus 
is a separate nerve, it has not been found supplying any of the sense organs ; while, even 
in the skate, the numerous branches for the sensory canals have been found springing 
directly or indirectly from the main trunk of the superficial ophthalmic division of the 
facial. This nerve (s.o.f., fig. 6), on leaving the buccal division of the facial, escapes from 
the cranium along with the ophthalmicus profundus, leaving which it runs forwards super- 
ficial to the orbital muscles, and reaches the snout by traversing a canal at the junction 
of the nasal capsule and the cranium. On the way it gives off sixteen branches, which 
penetrate the roof of the orbit. These, after dividing, enter the first (cranial) portion of 
the supra-orbital canal, and terminate in sense organs, probably twenty-three in number. 



SENSORY CANALS OF THE COMMON SKATE. 91 

As it runs along the side of the rostrum it gives off the twenty branches for the second 
(rostral) part of the canal ; while, as it passes through the cartilage in front of the orbit, 
it gives off a large branch (v.b., fig. 7) that curves outwards and downwards to break 
up into the forty-five twigs for the ventral portion of the supra-orbital canal — viz., sixteen 
for the inner part, twelve for the outer part, and seventeen for the looped part. This 
branch of the superficial ophthalmic comes into intimate relation with various branches 
of the buccal nerve. 

II. The Infra-Orbital Canal. — This canal (I.O., figs. 6 and 7), which, is continuous 
with the cranial portion of the lateral canal, and in communication with the supra-orbital 
canal, runs obliquely outwards between the eye and the spiracle, and then bending 
forwards runs for some distance nearly parallel to the supra-orbital canal. It next 
curves forwards and outwards to the margin of the snout, which it pierces to reach the 
ventral surface. It then runs backwards, communicating on the way with the supra- 
orbital, and on reaching the hy ©mandibular (HM., fig. 7) turns inwards, to dip into 
the naso-buccal groove. Emerging from the groove it soon unites with the corresponding 
canal of the opposite side, and forms a very short median portion (I.O. 7 , fig. 7) from 
which two canals curve sharply outwards, and then running forwards in close contact 
with the suborbital canals again unite near the tip of the snout (I.O. 8 , fig. 7). 

The infra-orbital canal includes the orbital, suborbital, orbito-nasal, nasal, half of the 
median, and the prenasal canals of Garman. The first (orbital) part of the infra-orbital 
canal seems to be a direct continuation forwards of the lateral canal. It has the same 
diameter and structure as the lateral canal. For the first 4 or 5 mm. of its course, it lies 
in a groove in the cartilage of the cranium, and afterwards is embedded in the fibrous 
tissue between the eye and the spiracle. As it bends forwards outside the eye it gives 
off a large tubule (t. 1 , fig. 6),* which runs backwards external to the spiracle, and opens by 
a terminal pore to the exterior. The portion of the canal which runs forwards in front of 
the eye (I.O. x -L0 2 ) lies immediately underneath the skin,, and slightly increases in size 
before passing to the ventral surface. The ventral portion may be said to consist of 
three parts : — (1) A straight part continuous with the hyomandibular canal, and in com- 
munication with the supra-orbital (I.0. 4 -L0. 5 ) ; (2) a looped part (L0. 5 -I.Q. 7 ), which 
runs inwards to the middle line posterior to the nasal capsule ; and (3) an inner part 
(I.0. 7 -L0. 8 , fig. 6 ; I.O., fig. 6a), which runs forwards almost in contact with the inner 
ventral part of the supra-orbital (S.O. 1 , fig. 6a). These three ventral segments lie em- 
bedded in the gelatinous tissue of the snout from 2 to 4 mm. from the surface, and possess, 
as a whole, a considerably larger lumen than the dorsal portion of the infra-orbital. 

As is the case with the supra-orbital, some parts are provided with, while other parts are 
without, tubules. The tubules in front of the eye (t.-t. ls , fig. 6), twelve in number, spring 
from the dorsal part of the canal. At first under a centimetre in length, they gradually 
increase up to two centimetres. Four of them (3-6) have a peculiar arrangement ; they 
connect the infra-orbital canal with the dorsal part of the hyomandibular (H.M. 5 , fig. 6), ; 

* This tubule Garman considered a branch of the main canal — a view not supported by it., structure. 



92 PROFESSOR J. C. EWART AND MR J. C. MITCHELL ON THE 

which later unites with an offshoot from the lateral canal. The third and fifth tubules 
terminate in the hyomandibular canal ; but the fourth and sixth, which are nearly 1'50 
cm. in length, simply communicate with the canal as they pass obliquely outwards. 

Passing to the ventral surface, the outer or straight part (suborbital and orbito-nasal 
of Garman) opens to the exterior by nine extremely short tubules (t.-t. 22 , fig. 7) ; the 
middle part (nasal of Garman) by seventeen tubules (t.-v. 33 , fig. 7), twelve short ones 
external to the naso-buccal groove, and five, slightly longer, internal to the groove ; and 
the inner (prenasal) part gives off, from about its middle third, eleven tubules (t.-t. m , 
fig. 7). The direction of the tubules is indicated in the figure. 

Innervation. — The first part of the infra-orbital canal is supplied by a slender nerve 
which springs from the buccal division of the facial as it separates from the superficial 
ophthalmic part of the facial. This nerve (6m. 1 , fig. 6) runs upwards posterior to the 
eyeball, and breaks up into six terminal branches, which enter the canal as represented 
in figure 6. For the next segment of the canal, two slender nerves spring from the 
buccal as it passes forwards under the eyeball. These nerves arch outwards, the first 
enters the canal nearly opposite the first tubule, the second by three branches opposite 
the origin of the three following tubules. To supply the middle portion of the canal on 
the dorsal surface a somewhat larger nerve springs from the buccal as it appears from 
under the eyeball. This nerve, as it turns outwards and forwards, breaks up into 
eleven branches, eight of which enter the canal opposite the eight remaining tubules, 
while three terminate in the canal immediatelv in front of the tubules. 

ml 

The buccal, having given off this branch, divides into an internal and an external 
portion — the inner (bu. 1 , fig. 7) runs forwards above the palato-quadrate cartilage, and is 
mainly concerned in supj)lying the inner buccal group of ampullae ; while the outer (bu. 2 , 
fig. 7) runs obliquely outwards, and sends the most of its fibres to the outer buccal group 
of ampullae. From this outer division of the buccal, a branch passes forwards and inwards 
to supply the remainder of the dorsal part of the infra-orbital canal, the branch pene- 
trating the canal by six slender filaments. Supplying the ventral part of the infra-orbital 
canal, as far back as its junction with the supra-orbital (S.O. 5 , fig. 7), are nine twigs, 
which spring from a second branch from the outer division of the buccal that usually, at 
first, accompanies the one just described. The remainder of the outer part of the canal 
(orbito-nasal) is supplied by six slender nerves which also spring from the outer division 
of the buccal. The outer division of the buccal thus supplies the outer straight ventral 
portion, and the anterior part of the dorsal portion of the infra- orbital, i.e., part of the 
suborbital and the orbito-nasal of Garman ; the rest of the suborbital and the orbital of 
Garman being supplied by branches which spring from the main trunk of the buccal as 
it passes forwards under the eyeball. 

The remaining ventral portion of the infra-orbital canal is supplied by the inner 
division of the buccal nerve. As the nerve reaches the anterior margin of the palato- 
quadrate cartilage it sends branches both outwards and inwards, while the main portion 
runs forwards to enter the inner buccal group of ampullae, from which a few fibres escape 



SENSORY CANALS OF THE COMMON SKATE. 93 

and run forwards all but in contact with the terminal portion of the ophthalmicus 
superficialis — the division of the facial with which the buccal was originally united. 
Two of the branches which proceed outwards from the inner division of the buccal 
supply the part of the canal lying between its junction with the hyomandibular canal 
and the inner margin of the naso-buccal groove. The part outside the groove receives 
seven twigs, the part which dips into the groove, six. Another branch breaks up into 
nine filaments for the part of the canal between the groove and the short commissure. 
This short expanded median portion receives as many as ten relatively large branches — 
five from the right and five from the left buccal nerve. The inner (prenasal) portion of 
the infra-orbital canal receives altogether twenty-six nerves from the inner division of 
the buccal as it runs along the rostrum ; eleven of these, which reach the curved part of 
the canal behind the tubules, are relatively large, while the fifteen which pass to the 
anterior two-thirds are more slender and further apart. It thus appears that the buccal 
nerve innervates nearly one hundred sense organs — ninety-eight terminal twigs having 
been traced in the specimen examined. 

The infra-orbital canal, though containing nearly one hundred sense organs only, 
opens to the exterior by forty-nine tubules. The two canals communicate with each 
other in front of the mouth, and also, as in Amia, at the tip of the snout, and by means 
of four of its tubules with the hyomandibular canal ; while, by its proximal end, it is 
continuous with the lateral and supra-orbital canals. In communicating with the lateral, 
and in having a commissure at the tip of the snout,* the infra-orbitals of the skate differ 
from those of Lsemargus ; they also differ in having a limited number of tubules — far 
fewer tubules than sense organs. 

III. The Hyomandibular Canal. — The hyoid portion of this canal, as in Lsemargus, 
is absent, but the distal part of the mandibular persists. The horizontal portion, on the 
other hand, has been greatly extended, forming a long loop under the pectoral fin ; and, 
with the help of an offshoot from the lateral, a long wide loop on the upper surface. 
Beginning where the infra-orbital bends inwards, the hyomandibular (HM., fig. 7) runs 
backwards, external to the branchial clefts, as represented in figure 7, to form the long 
ventral loop (HM. 1 , fig. 7). The outer limb, when opposite the mouth (HM. 2 ), curves 
inwards, and then runs forwards immediately outside the infra-orbital canal, to pierce 
the tissues inside the propterygium and reach the dorsal surface. Having gained the 
dorsal surface, it at once dilates, to form in some cases a club-shaped expansion (HM. 5 , 
fig. 6) — the end of which is connected, as already explained, by tubules with the infra- 
orbital canal. From this expansion the canal, now comparatively slender, curves out- 
wards and backwards for some distance along the margin of the pectoral fin, and then 
bends inwards to join a branch (scapular ; sc, fig. 6) from the lateral canal. This greatly 
extended hyomandibular corresponds to the angular, jugular, subpleural, and pleural 
canals of Garman. 

The inner limb of the ventral loop gradually diminishes in size as far as the middle of 

* The union of the prenasals at the tip of the snout is said by Garman not to take place in B. Icevis. 



94 PROFESSOR J. C. EWART AND MR J. C. MITCHELL ON THE 

the branchial region ; throughout the remainder of the inner loop, and the entire length 
of the outer loop up to where it approaches the beginning of the canal, the same diameter 
(about 2 mm.) is maintained. The part which runs forwards side by side with the first 
part of the hyomandibular and the outer part of the infra-orbital has a diameter of 3'2 
mm. The part in front of the gill region, like the part of the infra-orbital with which it 
is continuous, lies in gelatinous connective tissue, some 3 mm. beneath the surface ; the 
rest of the ventral loop occupies a very superficial position. There are extremely few 
tubules given off from the ventral loop. Between the junction with the infra-orbital 
and the gill region there are ten tubules (t.-t. n , fig. 7). Of these, the four anterior are 
very short and near each other, while the remaining six are from 1*7 to 5 mm. in length, 
and wider apart. From the outer limb of the ventral loop, only four tubules (t.-t. 15 , fig. 7) 
arise : these tubules are wide apart, and they vary considerably in length and position, as 
shown in figure 7. 

The dorsal extension of the hyomandibular canal is at first somewhat dilated, and at 
some distance (about 3*5 mm.) from the surface; the remainder, which is flattened and 
has a small lumen, occupies a superficial position, and takes an irregular course towards 
the outer angle of the pectoral fin before it bends inwards to join the scapular branch of 
the lateral canal. The expanded anterior portion does not open directly to the exterior, 
but it has two tubules from the infra-orbital opening into its wide inner end, and two 
infra-orbital tubules open into the canal as it leaves the dilatation. From the long part 
of the canal that runs backwards over the ampullary canals to eventually end in the 
offshoot from the lateral canal, thirty-nine tubules (t.-t. 5i , fig. 6) were given off in the 
specimen figured. These, as the drawing indicates, are relatively numerous, and of 
varying lengths. They all run outwards, the majority outwards and backwards. 

The two mandibular portions of the hyomandibular canals form a single canal behind 
the mouth. They lie immediately beneath the thin skin covering the mandible ; and 
they together give off twenty-six short tubules (t.-t. m , fig. 7) which open by a row of 
minute pores posterior to the openings of the mandibular ampullary canals. 

Innervation. — The entire length of the hyomandibular canal (including the ventral 
loop, the long dorsal extension, and the mandibular part) is innervated by the hyo- 
mandibular branch of the facial nerve. This large nerve {Jim., fig. 6), as it approaches the 
hyoid group of ampulla? (H.A., fig. 6), breaks up into numerous branches, the majority of 
which terminate in the ampullae. Some of the branches for the sensory canal leave the 
nerve before it enters the ampullary capsule, while others pass through between the 
ampullae, and then radiate to the dorsal and ventral portions of the canal. 

The part of the canal in front of the hyoid group of ampullae is almost entirely 
supplied by branches which leave the nerve before it enters the ampullary capsule. 
From these branches nine nerves were given off to the anterior part of the hyomandibular 
canal (fig. 7). The whole of the long ventral loop, with the exception of the curve formed 
by the outer limb and the straight part that lies alongside the infra-orbital canal, is 
supplied by branches of the hyomandibular nerve, which penetrate the ampullary capsule 



SENSORY CANALS OF THE COMMON SKATE. 95 

(fig. 7). The main branch runs backwards nearly parallel with the inner limb of the 
loop. From this branch (1) slender twigs reach and penetrate the middle third of the 
inner limb, and (2) longer delicate filaments proceed to the posterior third of the inner 
and posterior half of the outer limbs. The rest of the outer limb, as far forward as 
the point where it begins to bend inwards, is innervated by four branches, each of which 
has a separate exit from the ampullary capsule. The bend formed by the outer loop 
receives its nerves from the precapsular branches, which reach it by passing under the 
anterior portion of the canal. The straight, most anterior, ventral portion, and the 
dilated anterior portion on the dorsal aspect, are supplied from a large superficial pre- 
capsular branch which runs directly forwards and divides into two main branches (hm. 2 , 
fig. 6). The outer dips downwards and sends six twigs to the ventral part ; the inner 
sends a long slender branch forwards which gives six twigs to the longitudinal part of 
the dilatation, and a short branch inwards, which sends several twigs to the transverse 
part of the dilatation. From the same precapsular branch three filaments proceed to 
supply the part of the canal immediately beyond its connection with the suborbital 
tubules. The next segment of the canal, the part from which the second to the four- 
teenth tubules are given off, is supplied by twelve twigs which radiate from a second 
precapsular branch. The rest of the dorsal portion of the hyomandibular canal is supplied 
by four branches, which escape from the capsule and break up into long, delicate fila- 
ments as they run outwards and backwards. This part of the canal gives off twenty-five 
tubules, and is penetrated by twenty-seven nerves, most of which enter near the origin of 
the tubules ; the two last nerves enter the terminal part of the canal which runs inwards 
to communicate with the anterior (scapular) offshoot from the lateral canal. 

The mandibular canal is supplied by a branch (hm. 1 , fig. 7) of the hyomandibular 
nerve, which leaves it and passes downwards between the first branchial chamber and the 
jaw muscles. This branch, after parting with the majority of its fibres to the mandibular 
ampullae (M. A., fig. 7), runs along the'posterior border of the mandible, and sends thirteen 
filaments to the sense organs of the canal. 

The hyomandibular canal, with its remarkable ventral loop (subpleural of Garman) 
and its long dorsal extension (pleural of Garman), has many points of interest. In the 
first place, these pleural or pectoral extensions are characteristic of the Batoidei. In all 
of them the dorsal extension, which bends backwards to join the scapular branch of the 
lateral canal, is invariably present ; and, except in the torpedoes, the ventral extension is 
also present, though in some of them, e.g. Raja ocellata, the outer limb of the loop is 
absent. Sappey's description of what may be called the pectoral portions of the hyo- 
mandibular canal is in many respects remarkable. Having failed, apparently, to establish 
a connection between the ventral and dorsal portions of the canal, he describes the 
ventral loop as forming the external and internal branches of the ventral mucous canal, 
which he describes as beginning near the front of the snout and extending backwards 
and then forwards to terminate near its origin. The inner limb is thus made to include 
the ventral part of the infra-orbital, which he evidently failed to discover was continuous 

VOL. XXXVII. PART I. (NO 6). Q 



96 PROFESSOR J. C. EWART AND MR J. C. MITCHELL ON THE 

with the dorsal part, i.e., with what he calls the anterior part of the dorsal longitudinal 
canal. The dorsal portion of the hyomandilmlar he represents accurately enough as con- 
nected with the infra-orbital — his dorsal longitudinal canal. He makes no reference to 
the innervation of any of the cranial canals, and, like Monro, considers the hyomandibular 
division of the facial as a branch of the trigeminal. 

Garman, after pointing out that " the manner in which the Batoidei became possessed 
of the ' pleurals ' is a question of considerable interest," states that the " clue to the 
solution of the problem is to be seen in Chlamydoselachus " (5). He considers that the 
dorsal portion (pleural canal) was derived from the spiracular, and the ventral loop (sub- 
pleural canal) from the jugular. Elsewhere he says, " No doubt the pleural originated 
as a branch of the orbital." Why Garman should suppose the " pleurals " originated 
from the "orbital" (i.e., the first portion of the infra-orbital) canal, it is difficult to under- 
stand. Some of the tubules of the infra-orbital open into the dorsal extension, and in 
some cases, e.g. JR. ocellata, this dorsal portion is disconnected from the ventral portion. 
But, on the other hand, both the ventral loop and the long dorsal extension are supplied 
by the hyomandibular nerve ; and when the canals are examined in embryo skate, and 
in the less specialised members of the Batoidei group, it becomes evident that the ventral 
loop (subpleural) has been formed by a backward extension of the hyomandibular canal, 
which turned upon itself (in some cases before reaching the level of the first branchial 
cleft), and grew forwards to penetrate the snout and then proceed backwards along the 
margin of the pectoral fin, thus forming, first, the ventral, and afterwards the dorsal 
loop. 

IV. The Lateral Canal. — This canal has been frequently figured, and more or less 
accurately described. Hitherto, it has usually been looked upon as beginning in the skate 
at or uear the temporal commissure. The commissure has been said to consist of two canals 
(the aurals), and the part between the end of the commissure and the supra-orbital canal 
has been described as a separate canal (the occipital.) But, as the commissure and the 
whole of the longitudinal canal, including its branches, from the beginning of the supra- 
orbital to the tip of the tail, is innervated by one nerve, viz., the lateralis division of the 
vagus, we shall consider the lateral canal as including in addition to the trunk portion, 
the commissural portion and the part immediately in front of it. 

The first precommissural portion (occipital of Garman ; lp., fig. 6) runs backwards 
and inwards to the outer end of the temporal commissure. It has the same diameter as 
the cranial part of the supra-orbital, and lies for the most part in a groove in the cranial 
cartilage. 

The commissure (lc., fig. 6), formed by the union of two branches, one from each 
lateral canal, runs right across the cranium, immediately behind the auditory pores. It 
lies immediately beneath the skin and firmly adheres to it. Neither of those portions 
give off any tubules, nor do they open to the exterior by means of pores. 

The first part (L., fig. 6) of the lateral canal of the trunk, after running for a short 
distance directly backwards, forms a sigmoid curve, and reaches the supra-scapular 



SENSORY CANALS OF THE COMMON SKATE. 97 

prominence. At the anterior margin of the supra-scapula, it gives off a long (scapular) 
branch (sc, fig. 6), which runs backwards and outwards towards the margin of the fin, 
communicating on the way with the dorsal extension of the hyomandibular canal. A 
second (post-scapular) branch (p.sc, fig. 6) springs from the canal opposite the posterior 
margin of the scapula, and runs backwards in a similar direction to the first (scapular) 
branch. The main canal having given off the posterior scapular, curves inwards, and 
runs along first the trunk, and then the side of the tail, terminating at or near its tip. 
The lateral canal and its scapular branches are flattened, and have a small lumen — the 
diameter diminishing as the tip of the tail is reached. 

From the part of the canal in front of the scapular branch there spring eleven tubules 
(t.-t. n , fig. 6) ; ten of these, which are of about the same length, curve inwards, and 
one, longer than the others, bends forwards and outwards. The part of the canal lying 
on the supra-scapula gives off no tubules, but from the origin of the post-scapular branch 
to the tip of the tail tubules are regularly given off. These tubules, which first run 
backwards and outwards, and afterwards backwards and inwards across the canal, 
gradually diminish in length from before backwards. The scapular branch gives off twelve 
tubules before, and fourteen after, communicating with the dorsal part of the hyomandi- 
bular canal. The inner tubules, which are of considerable length, run outwards and 
forwards, while those beyond the junction run almost directly outwards. The latter 
gradually diminish in length, and lie nearer each other than the former. 

The post-scapular branch gives off twenty tubules, which arch outwards ; the last eight 
rapidly diminish in length as the end of the canal is reached. 

Innervation of the Lateral Canal. — The precommissural and commissural portions, 
and the part of the trunk portion of the canal up to near the origin of the scapular branch, 
are supplied by a special nerve which springs from the lateralis division of the vagus at 
or near its ganglion. This branch passes upwards behind the auditory capsule, and as it 
approaches the surface breaks up into three bundles. One runs forwards to innervate 
the precommissural, another bends inwards to the commissural part of the canal, the 
third passes backwards at some distance below and to the outer side of the first part of 
the trunk portion of the canal, which it supplies as far as its eighth tubule (fig. 6). 
For the part of the canal immediately in front of the scapular branch, the two scapular 
branches, and the short part of the main canal between them, the lateralis gives off two 
special branches. The first, a fairly large nerve, springs from the lateralis in front of the 
shoulder-girdle, and, after approaching the surface, runs backwards and outwards immedi- 
ately behind the scapular branch of the canal. It sends three twigs to the main canal in 
front of, and a similar number to the main canal behind, the scapular branch ; and, as it 
accompanies the scapular branch outwards, it gives off thirty-two twigs, the majority 
of which enter the canal opposite the tubules (fig. 6). The second, or post-scapular 
nerve, springs from the lateralis as it reaches the posterior border of the shoulder-girdle. 
Having sent a twig to the main canal, it proceeds outwards behind the post-scapular off- 
shoot, to which it contributes twenty-four twigs, the greater number of which enter 



JH PROFESSOR J. C. EWART AND MR J. C. MITCHELL ON THE 

opposite the tubules (fig. 6). No other large, branches proceed from the lateralis nerve. 
As it proceeds backwards, first at some distance from the canal, but afterwards in close 
contact with it, the lateralis gives off slender branches which either directly, or after 
dividing, enter the canal to terminate in the sense organs. 

The Histology of the Sensory Canals. 

Many investigators have studied the minute structure of the lateral sense organs of 
fishes, but to Leydig (8), Merkel (4), Solger (9), and Fritsch (6) we are most indebted 
for information on this subject. In this paper it will only be necessary to give a short 
account of the minute structure of the canals of the skate. 

Hitherto it seems to have been taken for granted that the cranial canals differed in 
structure from the lateral canal. This, however, is not the case ; for in the skate, for 
example, some parts of the cranial canals exactly agree in structure with the canal of the 
trunk. It would be more accurate to say that the canals of the dorsal surface differ in 
structure from the canals of the ventral surface ; but even to this statement there are 
exceptions, for the anterior (rostral) part of the supra-orbital canal and the anterior dorsal 
part of the infra-orbital canal, as well as the dilated dorsal portion of the hyomandibular 
canal, all differ from the canal of the lateral line, and agree with the canals of the ventral 
aspect. Apparently the difference in structure depends on the relation of the canals to 
the skin ; for the canals which are imbedded in, or lie immediately in contact with, the 
skin, differ from those that lie more or less deep in the subcutaneous tissue. The canals 
intimately related to the skin, i.e., the lateral canal, and, with the exceptions just 
mentioned, all the dorsal cranial canals, are flattened, have a small lumen, and are to a 
large extent composed of fibro-cartilage. 

The ventral canals and the portions of the supra-orbital, infra-orbital, and hyomandi- 
bular already specified, have, on the other hand, a rounded form ; the lumen is often five 
to six times greater than that of the lateral canal, and there is little or no fibro-cartilage 
in the wall. Further, while the wall of the ventral canals is of nearly the same thickness 
all round, the wall of the lateral canal, and of the cranial canals which resemble it, while 
presenting thick fibro-cartilaginous sides, have only a thin roof and floor. It may here be 
mentioned that Fritsch (6) gives a figure of a " trunk canal" of the torpedo, and states 
that while the trunk canals are fibrous, the head canals bear a fibro-cartilaginous character. 
This may be true of the torpedo, but it does not hold for the skate. 

The Dorsal Canals. — The lateral canal may be taken as an example of what might be 
known as the dorsal or cutaneous type, while the ventral part of the infra-orbital may 
serve as an example of the wide, thin-walled ventral or subcutaneous type. The lateral 
canal, which lies either in or immediately beneath the skin, is flattened, and somewhat 
resembles a long narrow slightly tapering ribbon, having one of its surfaces parallel with 
the surface of the skin. The small lumen occupies less than a third of the width of the 
ribbon ; and, while it is bounded at each side by a thick fibro-cartilaginous wall, the floor 



SENSORY CANALS OF THE COMMON SKATE. 99 

and roof agree in consisting of a thin layer of fibrous tissue with at the most a few car- 
tilage cells. The roof is translucent ; hence, when a canal is exposed, the position of the 
lumen is at once evident, presenting quite a different appearance from the dense lateral 
walls. 

The thin, fibrous roof and floor, and the thick, fibro-cartilaginous lateral walls, and the 
sense organ, are shown in figure 8. The sense organ (s.o.), it will be observed, stretches 
almost right across the inner wall. Usually the tubules run obliquely through the 
wall, and the fibro- cartilage extends along each tubule to within a short distance of 
the external aperture. Beyond the cartilage the tubule consists of epidermal cells, 
with pigment cells interspersed ; these pigment cells, by forming a dark ring, often 
indicate the position of the terminal pore. 

The sense organs throughout the greater part of the lateral canal do not, as might be 
expected, lie in the floor ; but, as shown in figure 8, in contact with the inner lateral 
wall. In front of the shoulder-girdle they are either on the side of the canal or on the 
roof. 

The canals (with the exception of the parts occupied by the sense organs) and the 
tubules are lined with two layers of epithelial cells. The deeper layer consists of rounded 
and somewhat irregular cells which rest on a basement membrane, and are often separated 
by intercellular spaces containing leucocytes. 

The superficial cells are columnar in form ; in most cases they are short and broad, 
having the free outer end non-granular, and the deep end occupied by the nucleus. 
These columnar cells, though resembling mucin-forming cells, were never seen assuming 
the goblet form, or giving evidence of being actively concerned in the production of 
mucus. They contrasted strongly with the goblet cells which exist in great numbers in 
the epithelium of the skin (fig. 8) ; and, undoubtedly, produce the abundant coating of 
mucus always present in the skate. 

In longitudinal and transverse sections through the areas occupied by the sense 
organs, it is observed that, as the sense organ or hillock is approached, the deeper layer 
of cells disappears, while the superficial layer assumes the form of long narrow columns, 
each with a nucleus near the middle of its length. These columnar cells form_ a well- 
marked zone around the sense organ proper — a zone sometimes fifteen cells wide. The 
sense organ which lies within this zone consists of sense cells, supporting cells, and of 
highly refractile processes, which project into the hillock from the basement membrane. 

The sense cells, which are of a cylindrical form, lie within and between the support- 
ing cells. Each has a large nucleus near its deep, inner end, and a hair-like process 
projecting from its outer end. These hair cells are less numerous than the supporting 
cells, which lie between and around them. The supporting cells, especially towards the 
centre of the hillock, are long and narrow, and thus differ from the short and compara- 
tively broad cells which line the canal and the hair cells already mentioned. The pro- 
cesses which project into the hillock from the basement membrane Solger describes as 
" zwischen-pfeiler" (9). They seem to extend from between the inner ends of the support- 



100 PROFESSOR J. C. EWART AND MR J. C. MITCHELL ON THE 

iug cells to the top of the hillock, and thus they in a way resemble the Miillerian fibres 
of the retina. 

Besting on the top of the hillock there is often what Solger terms the " cupula- 
bihlunof." This seems to consist of mucin. In some cases we have seen long threads of 
mucin extending from the hillock into the cupula or across the canal, the threads having 
frequently leucocytes entangled between them. 

Each sense organ has a nerve passing to it. The nerves, usually accompanied with 
one or more capillaries, enter the canal a short distance from their respective sense organs, 
and run obliquely through the eanal to break up under the hillock into a number of 
terminal fibres which seem to end in close connection with the hair cells. 

With the exceptions already mentioned, the dorsal canals have the same structure as 
the lateral canal. 

But, while the sense organs and tubules have a metameric arrangement in the trunk, 
there is no relation between the sense organs and segments in the head region ; and, as 
already pointed out, some portions of the cranial canals, though possessing numerous 
sense organs, have no tubules connecting them with the exterior. 

In all the cranial canals, both dorsal and ventral, there are far more sense organs than 
segments, e.g., in the supra-orbital canal there are nearly ninety sense organs, and in the 
infra-orbital there are over ninety. Why the sense organs of the head are so numerous, 
may be understood should we in course of time discover the function of the lateral sense 
organs. 

The writers who assert that the sense organs and tubules agree in number have 
probably only directed their attention to the sensory canals of sharks ; for certainly, as 
figures 6 and 7 clearly show, there are long stretches of canals with few or no tubules. 
As to whether in the embryo the tubules are more numerous than in the adult we have 
no information. If there are more tubules in the embryo than in the adult, it may 
be inferred that the parts of canals that have lost their tubules are in process of 
degenerating — of being reduced to vesicles, such as take the place of the ventral sensory 
canals in the torpedo. 

The Ventral or Subcutaneous Canals. — In these canals, which have usually a lumen 
five or six times greater than that of the dorsal canals, the wall is of uniform thickness, 
and composed of a thin layer of fibrous tissue (fig. 9). Like the dorsal, they are lined by 
two layers of cells, except at the sides of the sense organs. The sense organs only differ 
from those of the dorsal canals in being slightly larger, and in having a wider zone of 
columnar cells surrounding them. 

It may be mentioned that in a very young skate we had the opportunity of examining 
the lining cells, and to a certain extent the sensory cells differed from those of the adult. 
The two layers of cells which line the canals closely resemble each other ; and, as the 
sense organ is reached, the layers separate, the deeper one passing under the hillock, while 
the superficial becomes continuous with the supporting cells. The sensory cells are pear- 
shaped, and have oval nuclei, while the supporting cells are long and narrow. 



SENSORY CANALS OF THE COMMON SKATE. 101 



The Sensory Follicles or Pit Organs* 

The sensory follicles (" spalt-papillen " of Fritsch), as already indicated, lie in relation 
to the lateral and infra-orbital canals. Those related to the lateral canal form a row 
which extends from the region of the supra-scapula as far as the first dorsal fin — one for 
every two segments. The follicles lie between the lateral line and the middle line of the 
trunk and tail (p.o., fig. 6). 

The second group consists of two follicles (p.o. 1 , fig. 6) which lie in front of the audi- 
tory pores ; while the third group consists of five follicles (p.o. 2 , fig. 6) which lie external 
to the eye, immediately within the infra-orbital canal. The follicles though small are 
quite visible without the assistance of a lens in fresh specimens, especially when the 
epidermis is removed with the edge of a scalpel from the slight papillae by which they 
open on the surface. With the help of a lens, the groove or split which runs across the 
papilla, and leads into the pit, becomes evident. In those related to the lateral canal, and 
the two in front of the auditory pores, the split is at right angles to the long axis of the 
fish ; while in those lying within the infra-orbital canal, the split is nearly parallel to the 
long axis. 

In uninjured specimens, each follicle is seen to present externally a slight rounded 
projection, divided into two by a fissure which leads into the pit or follicle proper. 

The elevation consists chiefly of layers of epithelial cells, amongst which are many 
goblet cells. In vertical sections the epithelial layer, still containing goblet cells, is seen 
to extend well into the follicle. The bottom of the follicle is occupied by a large rounded 
sense organ (fig. 10), which in many respects resembles a taste-bud. The sense organ 
consists of pear-shaped sensory cells, with large oval nuclei and hair-like processes at the 
outer end of each cell. The sensory cells are surrounded by columnar supporting cells, 
in which the nuclei are deeper than in the hair cells. Passing to the sense organ of each 
follicle are several nerve fibrils. These fibrils pass obliquely upwards through the 
epidermic cells which underlie the follicle, aud terminate in the sense organ. The nerves 
for the trunk follicles seem to come from the lateralis, those for the infra-orbital group 
from the buccal, while those for the two follicles in front of the auditory pore may either 
arise from the lateralis nerve or from the glossopharyngeal — this is a point we have not 
been able to settle. We look upon these follicles as homologous with the pit organs of 
Amia. Merkel states they have been found in Mustelus and Squatina. 



102 PROFESSOR J. C. EWART AND MR J. C. MITCHELL ON THE 



BIBLIOGRAPHY.* 

(1) Ewart, "The Sensory Canals of Laemargus," Roy. Soc. Trans. Edin., vol. xxxvii. part i. p. 59. 

(2) Ewart, "The Cranial Nerves of Elasmobranch Fishes," Roy. Soc. Proc, vol. xlv., 1889. 

(3) Sappey, Etude sur Vappareil mucipare, &c, 1879. 

(4) Merkel, Ueber die Endigungen der sensiblen Nerven in der Haut der Wirbelthiere, Rostock, 1880. 

(5) Garm&n, "On the Lateral Canal System of the Selachia," Bull. Mus. Comp. Zool, Cambridge, Mass., 

vol. xvii. No. 2. 

(6) Fritsch, Die Electrischen Eiscke Die Torpedineen, Leipzig, 1890. 

(7) Allis, "The Anatomy and Development of the Lateral Canal System of Amia calva," Journal of Morpho- 

logy, vol. ii., 1889. 

(8) Leydig, Lehrbuch d. Histologie des Menschenu. d. Thiere, 1857. 

(9) Solger, "Neue Untersuchungen zur Anatomie der Sectenorgane der Fische," Arch, fur mikro Anat., 

1879-80. 



EXPLANATION OF PLATES.— PLATE I. 

Fig. 1. The sensory canals of the head and part of the lateral canal of the trunk, and the nerves which 
innervate their sense organs. The position and relations of the various canals and nerves have 
been represented as accurately as possible from actual dissections. 

S.O.-S.0. 4 , The supra-orbital canal. S.O., where the canal begins on the dorsal surface in connection 
with the infra-orbital; S.O. 1 , the middle of the great dorsal outward curve ; S.O. 2 , where the canal 
dips into the snout to reach the under surface ; S.O. 3 , the canal as it arches over the nasal capsule ; 
S.O. 4 , the end of the supra-orbital canal communicating with the infra-orbital. The tubules by 
which the canal communicates with the exterior are shown on the right side ; the ventral part of 
the canal is represented by dotted lines. 

s.o.f, The superficial ophthalmic branch of the facial nerve. On the right side it is represented as 
giving off numerous branches which enter the canal and terminate in the sense organs (hillocks) ; 
.s.o./. 2 , the deep or ventral branch which supplies the distal portion of the supra-orbital canal. The 
ophthalmic branch is represented as being intimately related at its origin with the buccal (bu.) and 
hyomandibular (lim.) branches. The fibres which supply the ampullae of the ophthalmic group of 
ampullary canals are not figured, s.o.f. 1 , the ganglion of the superficial ophthalmic branch of 
the facial. 

I.O.-I.O. 5 , The infra-orbital canal. I.O., the infra-orbital in contact with the supra-orbital; 
I.O. 1 , where the canal, after it has reached the ventral aspect, communicates with the hyo- 
mandibular (HM.) ; I.O. 2 , where it communicates with the supra-orbital; I.O. 3 , the ventral loop ; 
I.O. 4 , where the two infra-orbitals meet in the middle line; I.O. 5 , the infra-orbital terminating at the 
front of the snout. The tubules are as far as possible represented on the left side of the figure ; 
the ventral tubules have been represented as running obliquely outwards, but in reality the majority 
of them project directly downwards from the under surface of the canal, ot., the (otic) part of the 
infra-orbital canal continuous with the lateral canal (Ip.) ; bu., the buccal branch of the facial; on 
the left side, the buccal branches to the infra-orbital canal are shown ; ot.n., the branch to the otic 
portion of the infra-orbital springing from the buccal ganglion (bu.gl.) ; 6m. 1 , the inner branch of the 
buccal which supplies the greater part of the canal beyond its connection with the supra-orbital, 
and also the inner buccal group of ampullae ; bu. 2 , the outer branch of the buccal which sends the 
most of its fibres to the outer buccal group of ampullae. 

1IM.-HM. 1 , The Hyomandibular canal, inn., the hyomandibular branch of the facial with its 
ganglion (hm.gl.). It sends most of its fibres to the hyoid group of ampullae, but a slender branch, 
km. 1 , supplies the sense organs of the hyomandibular canal. 

* A more complete list will be found appended to the paper on Lsemargus. 



SENSORY CANALS OF THE COMMON SKATE. 103 

~L.lp.lc, The lateral canal. lp., the most anterior part continuous with the otic portion of infra-orbital ; 
lc., the commissure connecting the two canals ; L., the anterior portion of the trunk canal — the 
tubules are shown on right of figure ; I., the lateralis nerve arising above the level of the glosso- 
pharyngeal nerve ; l.gl., the ganglion of the lateralis ; I. 1 , the first branch passing to the sense organs 
of the commissure and the precommissural part of the lateral canal — this branch may contain 
some glossopharyngeal fibres ; I. 2 , the second branch supplying sense organs of anterior part of 
trunk canal; n.a., nasal aperture; E., eye; sp., spiracle; mo., mouth; l.f., labial fold ; a.p., auditory 
pores ; fa., facial nerve — the homologue of facial in higher vertebrates ; pi., its palatine branch ; 
ps., pre-branchial, and p.b., post-branchial branches; s./.,the most superficial root fibres of facial, 
some of which pass to all three supra-branchial nerves — these fibres probably innervate the 
ampullae of the ampullary canals ; v.gl., large ganglion of vagus with which the branchial branches 
(b^-b. 4 ) and the intestinal branch are connected. 

PLATE II. 

Fig. 2. Diagram to indicate the distribution of the dorsal branches of the cranial nerves. Pr., Ophthalmicus 
profundus, springing from brain in front of the trigeminal (Tr.) ; o.n., root of profundus (oculo- 
nasal) ; o.n.g., ganglion of profundus ; o.n. 1 , dorsal branch of profundus ; I.e., long ciliary branches ; 
or., orbital branch ; l.r., long root of ciliary ganglion ; o.m., deep branch of oculo-motor giving off 
short root (s.r.) of ciliary ganglion (e.g.) ; s.c., short ciliary nerves passing to eyeball. 

Tr., Trigeminus, t.r., trunk of trigeminus near Gasserian ganglion (G.) ; s.o.t, dorsal or superficial 
ophthalmic branch of trigeminus ; mx., maxillary (pre-branchial) branch ; mi, mandibular (post- 
branchial) branch ; mo. , mouth. 

Fa 1 ., Four roots, the fibres of which are rearranged to form the three supra-branchial branches 
of the facial (the superficial ophthalmic, buccal, and hyomandibular), which innervate the five 
groups of ampullae, and the supra-orbital, infra-orbital, and hyomandibular sensory canals. 

Fa., Root of the nerve which corresponds to the facial of higher vertebrates. It lies in contact 
with, and receives a communicating branch from, the auditory nerve (Am.). 

s.o.f., The first dorsal branch of facial — the ophthalmicus superficialis — which supplies the supra- 
orbital canal (S.O.), the superficial ophthalmic group of ampullae (S.O.A.). s.o.f. 1 , the ganglion; 
s.o.f. 2 , the ventral branch passing to the terminal portion of the supra-orbital canal (S.O.). 

bu., The second dorsal branch of facial — the buccalis — which supplies the infra-orbital canal (I.O.), 
and the inner (LB. A.) and outer (O.B.A.) buccal groups of ampullae. bu., the ganglion on 
the buccal nerve, from which a branch springs to supply the proximal part of the infra-orbital 
canal ; bu. 1 , the inner division of the buccal which innervates the inner buccal group of ampullae 
(I.B.A.) and the greater part of the infra-orbital canal beyond its connection with the supra- 
orbital ; bu. 2 , the outer division of the buccal which supplies part of the infra-orbital canal and 
the outer buccal group of ampullae (O.B.A.); km., the third dorsal branch of facial — hyomandi- 
bularis — which innervates the hyoid and mandibular groups of ampullae, and the hyomandi- 
bular canal, including the ventral loop, the dorsal extension, and the mandibular part, when 
present; h.g., the ganglion of the hyomandibular lying in contact with the ganglion of the 
facial proper (fa.); hm. 1 , the large branch for the hyoid group (HA.) of ampullae; hm?, the 
branch which supplies the mandibular group of ampullae (M.A.), and the mandibular canal (m.c.) — 
the mandibular offshoot and the mandibular group of ampullae are both absent in Laemargus ; 
sp., spiracle. 

fa., The homologue of the facial of higher vertebrates, pi., palatine which passes from the ganglion 
to roof of mouth; p.s., pre-branchial fibres to the spiracle ; p. b., post-branchial branch which 
passes behind spiracle, and eventually reaches the mucous membrane over the hyoid arch; m.f, 
motor fibres which leave this nerve to supply some of the jaw muscles. 

Aw., The auditory nerve passing to the auditory apparatus (A.A.). a., auditory pore; GL, glosso- 
pharyngeal nerve arising under cover of the lateralis; gl., its ganglion, beyond which are the 
pharyngeal pre- and post-branchial branches ; gl., the dorsal branch represented as supplying 
VOL. XXXVII. PART I. (NO. 6). R 



104 PROFESSOR J. C. EWART AND MR J. C. MITCHELL ON THE 

(1) a short segment (T.T.) of the great longitudinal canal immediately behind the infra-orbital 
canal, and (2) a row of pit organs (p.o.). That the dorsal branch of the glossopharyngeal 
innervates sense organs and pit organs in Selachian as in Amia has not yet been demonstrated. 

T.T., The part of the longitudinal canal which the glossopharyngeal might be expected to innervate 
in a typical Selachian. This might be known as the glossopharyngeal or temporal canal. 1 br., 
first (glossopharyngeal) branchial cleft. 

La., Lateralis nerve, l.g., lateralis ganglion ; I. 1 , first branch passing to the temporal commissure 
(Lc), and the anterior part of the lateral canal (L.). 

I. 1 , Branch springing from the ganglion to supply part of the canal and the anterior follicles or pit 
organs (p.o.l.). l.n., the lateralis extending backwards, nearly parallel with the lateral canal (L.). 

W-V. 3 , The first three branchial branches of the vagus, each with a ganglion (II.-IV.), pharyngeal 
pre- and post-brauchial branches. 

V. 4 -V. 5 , The united fourth branchial and intestinal branches of vagus. V., ganglion of vagus IV. ; 

i.gl., ganglion at root of intestinal branch (i.n.) ; 2 br.-5 br., second to fifth branchial (vagus) clefts. 

Fig. 3. The Cranial Canals of Amia. This figure has been introduced to admit of a comparison between 

Amia and Selachians, and to indicate the new system of grouping the canals. The details are 

from a figure by Allis (30), with which it should be compared. 

S.O., Supra-orbital canal, s.o.f., superficial ophthalmic of facial supplying the canal and a row of 
pit organs (s.p>). 

I.O., Infra-orbital canal, ot.n., the otic branch of facial which supplies the sense organs 15 and 16 
of the first segment {ot. ot. 1 ) of the infra-orbital ; bu., the buccal nerve supplying the infra- 
orbital canal, with the exception of the otic part. HM., the hyomandibular canal extending 
downwards from the proximal end of the infra-orbital to run along the mandible ; hm., the 
hyomandibular nerve supplying the hyomandibular and four rows of pit organs. 

T., Temporal canal lying between infra-orbital and lateral, gl. 1 , glossopharyngeal nerve supplying 
the single sense organ of the temporal canal and a row of pit organs ; gl., ganglion of glosso- 
pharyngeal nerve. 

L., Lateral canal beginning at the posterior end of the temporal and extending on to the trunk. 
I.e., supra-temporal commissure ; L, lateralis nerve ; I. 1 , first branch supplying commissure, a line 
of pit organs, and two sense organs of the main canal ; I?, second branch supplying a sense organ 
and a row of pit organs {p.o.) ; I. 3 , a third branch supplying the sense organ (21), which, according 
to Allis, lies at the junction of the infra-orbital and lateral canals. 
Figs. 4 and 5. Sensory Canals of Chlamydoselachus (after Garman). cr., r., sr. =* supra-orbital canal; orb., on., 
n., pn. = infra-orbital ; oc, au. = precommissural and commissural parts of lateral canal (/.); ang., 
angular; /., jugular; o., oval ; g., gular ; sp., spiracular — part of hyomandibular canal. 

PLATE III. 

Figs. 6 and 7. Sensory Canals of Rata batis. S.O.-S.O. 3 , Supra-orbital canal. S.O., proximal part ; S.O. 1 , 
beginning of rostral portion; S.O. 2 , point where canal penetrates snout to reach ventral aspect; 
S.O. 3 , S.O.*, ventral loop; S.O. 5 , canal joining infra-orbital; t. 7 , t. 23 , t. 33 , t. i5 , tubules. 

s.o.f., Superficial ophthalmic branch of facial with ganglion on root. It supplies supra-orbital canal 
and the ophthalmic group of ampulla?, v.b., ventral branch passing to sense organs of ventral 
portion of canal ; S.O. A, positiou of superficial ophthalmic group of ampullae. 

I.O.-I.O. 8 , Infra-orbital canal. I.O., canal continuous with lateral canal and communicating with 
supra-orbital ; I.O. 1 , sub-orbital portion ; I.O. 2 , canal passing to ventral surface ; I.O. 3 , beginning of 
ventral portion; I.O. 4 , its communication with supra-orbital; I.O. 5 , canal communicates with 
hyomandibular and bends inwards ; I.O. 6 , part of canal which dips into buccal groove ; I.O. 7 , union 
of two infra-orbitals in front of mouth; I.O. 8 , union of two infra-orbitals at tip of snout; 
t. 1 , t. 13 , t. 39 , t. &0 , tubules of canal; bu., buccal nerve with ganglion on its root, supplying infra- 
orbital canal and inner and outer buccal groups of ampullae ; bu.o., branch for first part of canal — 
this branch probably supplies the sub-orbital row of pit organs, p.o. 2 ; bu. 2 , outer division of buccal 



SENSORY CANALS OF THE COMMON SKATE. 



105 



passing to outer buccal group of ampullar; O.B.A., part of the dorsal and part of the ventral 
portion of the infra-orbital canal ; bu.\ inner division of buccal passing to inner buccal group of 
ampullae and the infra-orbital canal from its junction with the hyomandibular. 
HM.-HM. 7 , Hyomandibular canal. HM., canal communicating with the infra-orbital (I.O. 5 ) ; 
HM. 1 , end of ventral loop ; HM. 2 , outer limb of loop bends inwards ; HM. 3 , canal passing to 
dorsal surface ; HM. 4 , canal as it reaches dorsal surface ; HM. 5 , expanded part communicating 
with tubules of infra-orbital ; HM. 5 -HM. 6 , long dorsal extension which terminates in scapular 
offshoot from lateral canal ; HM. 7 , mandibular portion of hyomandibular canal ; t. n , t. 15 , t. bi , t. 67 , 
tubules ; km., hyomandibular nerve ; hm.g., its ganglion ; hrn. 2 , branches passing in front of or 
through the hyoid group of ampullae (H.A.) to innervate the sense organs of the various parts of 
the hyomandibular canal, with the exception of the mandibular portion ; lirn. 1 , branch for the 
mandibular group of ampullae (M.A.) and the mandibular portion (HM. 7 ) of the hyomandibular 
canal. 
L.-L. 3 , The lateral canal, l.p., the precommissural part, and I.e. the commissural part, of lateral 
canal ; sc, scapular offshoot ; p.sc, post-scapular offshoot ; p.o. 1 , lateral row of pit organs ; p.o., 
pit organs near the auditory pore (a.). 
l.-l. 2 , Lateralis nerve, l.g., its ganglion ; l.t., branch which innervates half of commissure (I.e.), part of 
lateral canal in front of commissure (l.p.), and anterior part of main canal ; l.sc, branch for scapular 
offshoot (se.) ; l.p.sc, branch for post-scapular offshoot ; Z.M. 2 , lateralis giving off branches to sense 
organs of lateral canal posterior to shoulder girdle. 

Fig. 6a. Transverse section through snout of young (just hatched) R. batis. S.O., supra-orbital canal 
(rostral part); S.O. 1 , ventral part of the same canal (subrostral) ; I.O., infra-orbital canal (prenasal 
part) ; r., cartilage of rostrum ; a.c, ampullary canals from superficial ophthalmic group of 
ampullae ; g.e., goblet cells of skin. 
Transverse section through lateral canal of a young (just hatched) R. batis, showing the thick 
cartilaginous lateral walls, and thin roof and floor, s.o., the sense organ on inner wall of canal ; 
g.c, goblet cells of skin, x 120. From a photograph. 
Transverse section through a ventral subcutaneous canal (ventral part of supra-orbital), showing the 
large sense organ (s.o.) lying in the roof of the canal, and some of the connective tissue in which 
the canal is embedded, x 300. From a photograph of a section of a R. batis 1 6 '5 cm. long. 

Fig. 10. Transverse section through a pit organ, showing the sense organ at the bottom of the involution. 
From near root of tail of a young R. batis. 



Fig. 8. 



Fig. 9. 



rar.s Roy Soc Ediir 



PROFESSOR EWART & J.C.MITCHELL, ON THE SENSORY CANALS OF THE COMMON SKATE. 



Vol. XXXVII 




: - - - - • -^ 



( 107 ) 



VII. — On the Latest Phases of Literary Style in Greece. By Emeritus Professor 

Blackie. 

(Read 4th April 1892.) 

In the two papers which I had the honour of reading to the Society in the spring of 
1890, my object was, in the first place, to combat the vulgar idea that modern Greek is a 
corrupt and barbarous language, almost as far removed from classical Greek as Italian is 
from the dialect used by Horace and Virgil ; and, secondly, to show that, between the 
two distinct strata in which Greek had flowed down continuously from Constantinople 
in a.d. 333 to the present day, — the literary structure used by educated men, and the 
Greek of the popular ballads used by the uneducated masses, — a compromise had been 
achieved by that great scholar and patriot, Adamantius Coraes. This compromise was 
made on the principle that the unity of action on which Greek nationality depends, 
requires that the learned classes should cheerfully adopt those few idiomatic peculiarities 
which had asserted themselves in the thought and expression of the great mass of the 
people ; while the great body of the language bore visibly the stamp of those whose 
genius in Church and State had shaped it forth in the Attic and Byzantine periods. On 
this basis the modern Greek language was left at the death of Coraes in 1833. But it is 
not to be imagined that a formative rule of this kind, in the mode of national speech, 
could be established at a stroke. All living language, like all living things, is a growth ; 
and besides, no exact law could be laid down for the limits of the compromise ; and the 
practical result of this giving and taking on both sides during the course of two genera- 
tions, from the establishment of the Greek kingdom in 1830 to the present hour, is what 
in this paper I intend to lay in some detail before the Society. Of course, in such 
circumstances there would naturally grow up two styles of literary expression, the one 
inclining more to the popular side, the other to the side of the higher culture ; and these 
two tendencies exist to the present hour, one class of writers inclining more to the 
•Xy&ala, or vulgar, and the other to the KaOapevovo-a, or the usage of classical purity. But 
though there are two distinct tendencies, with some intermediate shades of variation, it was 
not difficult to prophesy on which side, under the action of powerful forces, the ultimate 
preponderance would be. These forces were three : — first, the natural tendency of the 
lower stratum of society, in proportion as intelligence and education advance, to imitate 
the style of their social superiors ; second, the pride that the Greeks felt, especially after 
the glorious result of the War of Independence, in their inheritance of a language which 
had conquered the world by its wisdom, and triumphantly refused to be corrupted by 
centuries of Roman, Italian, and Turkish domination ; and third, perhaps most powerful 

VOL. XXXVII. PART I. (NO. 7). S 



108 EMERITUS PROFESSOR BLACKIE ON THE 

of the three, was the fact that the Greek of the New Testament was the Greek which 
regulated the services and the liturgies of the Greek Church, and which could no more be 
profaned by the corruptions of the vulgar tongue than the existing Scottish language, 
however excellent for popular ballads, could dare to show its face in a Scottish pulpit. 
How potently these purifying and elevating forces have acted can be shown in a very 
tangible way by merely taking a series of Greek publications in chronological order, and 
counting their gradually lessening deviations from the pure type of classical antiquity. 
Starting from the period previous to the great reform of Coraes, as a standard from which 
to measure the stages of advance, I find in twelve lines of the Erotocritus, a popular 
novel written in the Cretan dialect by Vicentius Kornares, published at Venice in 
the year 1756, twenty-four deviations from correct Greek; in the same number of 
lines of a Greek version of the Arabian Nights (Venice, 1792), nineteen deviations; 
and in the first five verses of the second chapter of the Gospel of Luke (Athens, 1824), 
covering about the same space, about the same number. Taking Coraes himself, in 
twelve lines of his familiar correspondence with a Smyrniote merchant, I count twelve 
deviations, and in another letter, only forty variations in three hundred and sixty lines, 
the reason of this difference being, plainly, that as the points of variation affect rather 
the connecting particles than the substantial material of the style, they are soon 
exhausted, and, on occurring twice, do not require to be numbered as special points of 
deviation. In Tricoupi's well-known History of the War of Independence (London, 
1833), such was the advance in identification with the correct Greek style, that in 
thirty- four lines I find only three marks of the influence of the vulgar tongue ; and in 
Rangabes' Drama of Ducas (Athens, 1874), only four such instances in twelve lines ; in 
a translation of Miss Agnes Smith's (now Mrs Lewis) Travels in Greece (Leipzig, 1885), 
I find eight in twelve lines ; while in twenty-four lines of Paspates' History of the 
taking of Constantinople by the Turks (Athens, 1890), only three deviations are found ; 
and of two Greek newspapers, the 'A/c^oVoXt?, October 1891, and the"A<7Tu, of December 
1891, the first shows only two variations in sixteen lines, and the second the same 
number in thirty lines. To the same most recent date belong the translation of 
Shakespeare's Hamlet, by Damirales (Athens, 1890), which, in twelve lines, shows only 
five small peculiarities of the vulgar style ; the Xpio-Tiavacou MeXerai, a religious magazine, 
at present issuiDg from the Athenian press, in which two whole pages, of forty lines each, 
contain only five ; lastly, in the Romaic New Testament, published by the Bible Society 
(Cambridge, 1890), I find in the first five verses of Luke ii. only six deviations from 
the pure type, as contrasted with nineteen in the version above quoted, before the day 
of political and literary regeneration. This is truly wonderful, and to be accounted for 
only from the operation of the powerful forces above mentioned, taken along with the 
spread of education in school and university, so characteristic of the intelligent Greek 
people. Nor do we do full justice to the advance when we merely count the quantitative 
amount of deviation from the pure style that occurs in this diminishing ratio ; we must 
look also at the quality. Well, the first thing that strikes us in this regard is the 



LATEST PHASES OF LITERARY STYLE IN GREECE. 109 

absolute banishment from the current literary style of every trace of foreign infection, 
such as used to be not uncommon in books some forty or fifty years ago. No man now 
writes <t7t>jti (from hospitium) for oIkos, <f>afii\ia for oiKoyeveia, or fiairopi for a steamboat ; 
even a tramway, the most recent of importations from England, is not a Tpa/j.a<s, but 
iTnro<ri§>ipoSp6fj.os, a horse railway, which you may laugh at as too polysyllabic a word for 
popular use-; but there it is, showing in the most determined fashion the instinct of the 
uncorrupted Greek tongue to borrow from nobody, when everybody is found to borrow 
from it. Taking even those types of the vulgar tongue, most of which do not appear in 
the current literary style of the day, how insignificant are their divergencies, and not more 
diverse from the style of Xenophon or the Greek plays, than the style of Xenophon or 
iEschylus differs from the style of Homer. AeV for ovk, for instance, is merely a natural 
curtailment for ovSev, — the accented syllable, according to a well-known law, being always 
retained. Ow for ova-i in the third person plural, present indicative, of verbs, plainly 
points to an old brotherhood with the Doric ovn and the Latin writ. The preference for 
verbal forms in v, as in yjivw and Svv<a, is plainly Homeric ; the loss of the infinitive mood 
and the optative, for which va for 'iva the subjunctive is regularly substituted, will cause 
neither surprise nor difficulty ; -rod for avrov, and to for avrw, is rather an improvement ; 
6 o-koios for o? and oamg, borrowed, no doubt, from the il quale of the Italian, has its 
analogies in the which and the whilk of our old English ; and if els be used for £v, and 
elvai for earn, and rjro for qv, these are mere grammatical peculiarities not greater than 
what occur in Pindar, and in the choruses of the Greek drama. Not a few of what 
certain nice modern scholars would call corruptions are no modern inventions at all, but 
as old as the foundation of Constantinople, or older ; and such words, if formed accord- 
ing to the native structure of the language, even though made yesterday, are not 
corruptions, but expansions and enlargements of the Greek speech. If, for instance, the 
modern Greek uses eixiropw for Suva/mat, he is as much entitled to do so as the ancients 
were to use airopu> or ov Svvafxai. But that the lust of innovation is not a fault with 
which modern Greek can largely be charged, is evident from the style of the New 
Testament, in which ixeOicrravw takes the place of /xe6l<7Tr]/j.i, and Iva, with the sub- 
junctive, habitually takes the place of the superseded optative, and not seldom also of 
the infinitive mood. 

So much for the triumph of what we may call the style of restorative purism in the 
current Greek language ; but there is a conservative party, and a party represented, as 
such a party requires to be, under such hostile influences, by men of distinguished 
literary eminence. And two such men, unquestionably, the party of the x<^°"' a 
SidXeKTos can boast, Bikelas and Polylas — the one a writer well known to the students of 
history by his excellent work on Christian Greece (Paisley, 1891), translated by the 
Marquis of Bute, as also by his Greek versions of some of Shakespeare's best plays ; and 
the other a Corfiote gentleman, who, besides a translation of Shakespeare's Hamlet, has 
given to the world a translation of Homer's Odyssey into Romaic. To give the 
classical scholar an idea of the degrees of departure from classical correctness exhibited 



110 EMERITUS PROFESSOR BLACKTE ON THE 

by these writers, as contrasted with the purist party, we cannot do better than set before 
him at length one of the most familiar passages in Hamlet, act i. scene 2, as translated 
by Polylas and Bikelas, and the same in the translation above named, by Damirales. 

" 0, that this too too solid flesh would melt, 
Thaw, and resolve itself into a dew ! 
Or that the Everlasting had not fix'd 
His canon 'gainst self-slaughter ! God ! God ! 
How weary, stale, flat, and unprofitable 
Seems to me all the uses of this world ! 
Fie on't ! fie ! 'tis an unweeded garden 
That grows to seed ; things rank and gross in nature 
Possess it merely. That it should come to this ! 
But two months dead ! — nay, not so much, not two : 
So excellent a king ; that was, to this, 
Hyperion to a satyr : so loving to my mother, 
That he might not between the winds of heaven 
"Visit her face too roughly." 

' Ax ! va tjpTropovcre tovt r\ tocto crTeper] adpKa 
va ^eiraywcru /ecu w? dxvog Spocrid va ylvrj ! 
t] tov vopov tov o IlAacrT>7? va pr\v e?xe orders 
va TifJLwprj tov avTO<povov ! Ge' pov, to Ge' pov, 
ttocto avouTa, koivu Kai dvuxpeXa icai a%peia 
tpaivovT bXa $ epe ra epy avTov tov Kocrpov ! 
QacriceXa va 'xovv ! K^7ro9 elvai xopTiacrpevog 
pes to ^ecnropiacrpd tov, Kai oXov tov yepicrav 
XOVTpoeiSrj <pVTa Kai £e(3XacrTapwpeva. 
Avtov va KaTavTwn ! 'AireOapevog poXig 
airo ovo pijvais ovoe tocto, ovoe kuv ovo. 
Ti e^alcriog (SacriXeas I Yirepiiov rJTav 

Kai TOVTO? C/ULTTpOCrOeV TOV SaTUyOO?" CO TTOCTO 

Tpvcpeptjv elx<e ayairrjv Tr)s pqTpos pov ! prjTe 
avepoi t ovpavov 6a vrrotpepve va irveovv 
CTKXr}pa s to nrpocrtoiTO Tt]S ! 

12 ! A? Tt]V ejiXeira avTtjv t^v CTTepedv Trjv crctpKa 
va eXvove, va 'crKopiri^e k era? cit/xo? va. yeivyl 
H vopov a? prjv topi£e 6 TiXacrTr)^ vd TraiSevfl 
tov avTOKTOvov ! — ' £1 Gee, Gee' /ulov, ttoctov Kovcpia 
kl avoocpeXrj Kai paTaia /a' avovaia Kai crairia 
pov (pacvovTai tu irpaypaTa tov Kocrpov tovtov oXa ! 
Ti crlxupa I tl crixapa ! Xwyoa0t x^P aov stvcu, 
^ecnropiucrpevov ! 'Fepicre dyKidOia Kai TpifioXovs 
ki ovo' ex ei a XXo TiTTore !...'? avTO vd KaTavTr\cr\\ ! 
M0X19 veKpo? irpo Svd pt]vwv . . . pr)Te Kav Svo ! "Ox* ' 
Ti pacriXevs ! Qpola^e pe tovtov octov 'poid^et 
o "Yirepiwv 6 Geo? pe ^aTvpov ! Kcu toctov 
yXvKog Trpos ty\v prjTepa pov, itov co? /ecu tov aepa 
Sev Oacpive '$ to irpocrwirov crKXypd vd t^? (pvcrrjcri^. 



LATEST PHASES OF LITERARY STYLE IN GREECE. Ill 

"CI, e'tOe va eTr/Kero, vet SteXveTO /cat etg Spocrov va peTe/3a\AeTO r) v-rrepdyav arepea avTr/ crdp£ ! 
"H va p.r) etxe Qecrir'tcret 6 Atwvtog tov Kara Trjg avToxetptag vo/xov\ 'CI 6ee\ Oee ! Uocrov oxXr/pa, 
ecoXa, Taireiva. ical avuxpeXrj p.ot (patvovTat to. tov koct/ulov tovtov ! 'E? tcopaicas ! EtVe yrj Ke^epcrco/xevr/, 
ev § (fivovTcu aypia yppra, KaTexpvcrt S' avTr)v crairpd /jlovov irp6.yiJ.aTa kou (pveret evTeXrj. Et? tovto 
v cnroXrj£fl ! Mo'At? Svo /Ar/vcov veicpog ! "Ofti, o%t, ovSe touov, ovSe Svo. BaertAeu? to&ov e^atpeTog, 
ocrTtg, crvyKptvo/xevog irpbg tovtov, tJto cog ' Yireptwv irpbg SaYi/poi/ !' Toa-ov 6e tjyatra Ttjv p.rjTepa fMOV, 
ware ovS' etg avrouf a/co'p>7 TOi/g dve/xovg tov Ovpavov >'/6eXev eTrtTpe^ret va Trvecocrt fitaioog eir\ tow 
irpocrcoTrov Trjg. 

To make the contrast complete, I may as well insert here a specimen of the prose 
style of Bikelas, with a passage from the columns of a current Greek newspaper. The 
extract from Bikelas is from a small volume (Athens, 1890), in which he gives to an 
Athenian audience his impressions of Scotland and its people. The extract relates to 
St Andrews, and the game of golf there practised. 

"0\t fJ-aKpav Trjg KCo/xo-woXewg Falkland, etg pudg irep'tirov topag dirocrTacriv Sia tov crtSr/poSpo/xov, 
KeiTai eir] Trjg OaXacrcrrjg r) apyaia iroXtg tov Aylov 'AvSpeov. Tr)v crrj/uiepov r) irdXig avTrj ^pt'ferat 
Sid Ta irapa Tr)v OdXaercrav ireS'ta ottov irai^eTat Sia er<patpoov to kot e^oxhv ^kcotikov iratyviov tov 
Golf. At icaicai yXcocrcrai Xeyow oti ol etpr/viKol ovtoi aycoveg diroTeXovv to cnroicXeicrTCKOv, rj TOvXa- 
X'cttov to icvpiwTepov Oe/xa 6/JiiXiag tcov r/crvxoov KaToiKCov Trjg. ' AXXore o/icog, KaTa. tov p.eaatwva 
Kpavyai iroXep.ov avTtJxW av TroXXaicig irepi Ta Tetxv Trjg /cat to al/xa eyyOr/ etg Tag oSovg T?)g. 

In this passage only five idioms distinctive of the popular dialect occur, viz. — 
ox' fo r ov, els for ev, t*]v o-r]p.epov for cr^fxepov, ow for overt, and rr/g for avTrjg ; nevertheless, 
it is sufficiently differentiated from the more advanced style of the "Ao-tv newspaper 
(Athens, 5th December 1891), in a passage of twice the length, containing a notice of 
the new Professorship of Modern Greek in the Liverpool College. 

'0 " 'Hpepjjcno? TaxvSpd/j.og Trjg AefiepirovXr/g" eSrj/xocrievcre irep\ Trjg etg to avToOt iraveirtdTrifxiov 
etaaycoytjg Trjg veoeXXqvtKrjg Tag eiroiJ.evag XeTTTOfiepetag ev tw tov 2a/3/3drou 23)2 Ae/cep/3ptou 0yXXw 
auToC, ct? /cat KaTaxwpi^o/Jiev &Se cog toctovto) /uaXXov evStaepepoverag, ocrw ev eTepatg x^P^? h eXXrjviKr) 
KXacrtKri Te /cat vewTepa Setvwg KaTairoXe/xelTat cog SrjOev rJKtcrTa xpWWog. 

MeTa 7rXeurTr]g burjg evxaptUTrja-ewg ayyeXXo/uev oTt r) ^vyKXrjTog Ttjg iraveirtcrTrjfiiaKrjg crxoXrjg 
a.7re<pacri<re tt\v ervcrTacrtv tStwv Tafjewv StSauKaXlag Trjg veag eXXrjvtKrjg yXuxrcrrjg ev Trj o")(,oXrj, irpocrXa- 
j3ovcra Sid ty\v StSacrKaXtav TavTtjv tov k. Kw^ctt. Kovp^, ocrrtg eirt tKavd fjor) eTrj eStSacricev ev Trj 
eXXr/viKi] KOtvoTrjTt Ai/3ep7rovXr)g. '0 /c. Kovp^?. e/c twv 'lovtcov vijercov ctywv to yevos, eive StaKeKptfjcevog 
§nrXcoiu.aTOVXog tov r Kave r Kt<jTY\fxiov 'AOrjvcov ical KaTOXog ov /jlovov Trjg eiritjTr/ixoviKtjg yvwerecog Trjg 
veoeXXr/vtKrjg yXw<Tcrr]g, aXXa Kat evpetag KXacrticrjg /xaOrjaeoog KaOcog /cat 7roXXcc>v evpunra't'icwv yXwcrcrwv. 
'YiXTrl£op.ev OTt r) crvyKaTaXe^tg StSdiCTOpog TOtavTrjg tKavoTr/Tog, dtag 6 k. JLovprjg, ev too aptOjuw tcov 
rj/ieTepcov evTOirtwv Kadr/yr]Tu>v, ecrTat crirovSatov irXeoveKTrj/ia Ty irave-KicrTr/txiaKr/ o"xoXr} /cat 8<peXog 
ov crp.iK.pov TOtg (poiTr/Taig avTrjg. H Ta£tg avTrj tov k. JLovprj ecrTat Kaircog d^ioirep'tepyog cog irpog to 
irpocrooiriKov avrr/g Kat TrtcrTeveTat OTt t) SiSacrKaXia avTOV OeXet crvvTeXecret to, p.eyicrTa irpog Kpe'iTTOva 
kou dicpi/3ecrTepav yvwcrtv Trjg veoeXXr/viKr/g yXoocrcrr/g irapa tcov cricovSaoTobv Tr/g AtfiepTrovXr/g. 

In this long passage there are only two points of the popular Eomaic idiom, 
viz. — elve for euTt, and the auxiliary BeXco with the future indicative ; and this 
suggests the important remark that it is by no means the intention of the advocates of 
the KaBapevovcra style to restore the classical idiom pedantically in all its detail ; they 



112 EMERITUS PROFESSOR BLACKIE ON THE 

merely aim at reducing its vulgarisms to a minimum, and retaining only as much of it 
as has become thoroughly engrained into the general structure of the language, and 
could not be extruded without violence. 

After this detailed exhibition of the two styles, the. only question that remains is 
how far the minority, as represented by these two eminent writers, are right, and on 
what grounds they justify their departure from the prevalent style approved by the 
great majority of their countrymen. On this head Bikelas says nothing ; but his motive 
must be, no doubt, the notion that when a man writes for the people, he must write in a 
style which the people understand. This, of course, is very proper as a general rule, but 
its propriety depends on circumstances ; and if the majority of the people, as seems 
plainly to be the case, prefer a style endeared to them by classical and ecclesiastical 
tradition, the argument loses its validity. There are in Greece two peoples and two 
dialects, just as there are in Scotland English and Scotch, each with its separate and 
well-marked sphere, but one of the pair for general currency universally allowed to 
dominate the other. But what does Polylas say? In the preface to his learned and 
scholarly translation of the play from which we have quoted, he says " that the essential 
character of the spoken language neither has been destroyed nor can be destroyed by 
any merely external changes ; its internal organism remains, which expresses the inborn 
inherent reason (evSidOerov \6yov), and breathes the living spirit of the people." This 
also is very true as a general principle ; but it seems somewhat too strong language 
to apply to the loss of the infinitive and the optative moods, and the use of auxiliary 
verbs in a few cases. Besides, may we not justly ask, Does not the organism of 
the upper stratum of the language, which came down in a continuous stream direct 
from Constantinople, express the character of Greek thinking and the internal organism 
of the Hellenic mind as much as the style of loose conversation and the popular ballad ? 
Then, again, further on he says that " while the structure of ancient Greek was decidedly 
synthetic, that of the modern dialect is as decidedly analytic." Here, again, we feel 
compelled to make the remark that the instances relied on, as the use of the auxiliary 
verbs, are too few to justify so large a conclusion and establish so striking a contrast. 
Greek has never, like English, lost its native power of holding by the wealth of its 
melodious terminations, and forming new compounds, when required, out of the fulness 
of its own vitality. 

So far, our verdict is decidedly in favour of the procedure of the immense majority of 
Greek writers from Coraes downwards — in favour, namely, of the tendency to abolish, as 
far as possible without pedantry, the gap that, a hundred years ago, separated the Greek 
of the common people from the Greek of the educated classes. In fact, without any 
reasoning at all about the matter, the spread of education and intelligence among the 
Greek people is filling up this gap day by day by an uncontrollable necessity. Of this 
I will give two instances from my own experience. When in Athens for the first time 
some forty years ago, a little girl, my landlord's daughter, was going down with me to 
the Piraeus to get a boat for Salamis. Looking down to the shore, I said to my little 



LATEST PHASES OF LITERARY STYLE IN GREECE. 113 

guide, 7rov ehai rj (3apKeTra — "Where is the boat?" " You should not say ^apKerra, sir," 
was the reply, " but XeV/3o?," — the genuine Greek word used by Thucydides, not an 
Italian word which reminded the little patriot of the departed days of Venetian domina- 
tion in the Morea. Another instance of the same patriotic purism occurred to me last 
spring in the case of a group of common schoolboys. I was standing on the pier of 
Nauplia, beside a train of cabs, waiting to take me and my fellow-voyagers to Mycense, 
when a crowd of these lively urchins, attracted by our appearance, gathered round us to 
stare at the strangers. Wishing to show them that I could speak Greek, and Greek that 
they could understand, not like the usual Englishmen's Greek, which, as old Thomas 
Fuller said, nobody understands but themselves, I said, pointing to one of the horses in 
the cab, 7ra>? ovo/ua^ei? to tyov touto — What is the name of this animal ? The reply 
jumped out forthwith, not as I expected in the popular " a\oyo" the unreasoning brute, 
but " tWo?," the old classical designation for the noble animal. Aev etvai '[-7nro$ elvai aXoyo, 
was my reply ; but they had been taught too well, and parried my thrust as emphatically 
as the little girl at the Piraeus. 

Of course, nothing in the above strictures should be interpreted to imply that the 
vulgar Romaic dialect is to be disowned altogether, and consigned to a limbo of intolerable 
barbarism. On the contrary, in its own sphere, in the sphere of the historical ballad and 
popular song, it is invaluable, and is, in fact, too closely bound up with the best patriotic 
recollections of 1821 to be willingly forgotten so long as (Greece remains Greece. 
Polylas, therefore, is right so far ; and, while the style of the popular ballads may carry 
with it associations which harmonise ill with the elevated style of such a serious and 
thoughtful tragedy as Hamlet, it may for that very reason be the best neo-Hellenic form 
in which to dress, as this author has done, the Odyssey of Homer (Athens, 1875), — a 
poem which partakes more of the easy breadth of a series of popular ballads, than of the 
sustained majesty of such lofty epics as those which have immortalised the names of 
Virgil and Milton. 

In conclusion, as a practical man, and of half a century's experience in the educational 
treatment of languages, I take the liberty to make the following threefold application of 
the living power of the living Greek language as set forth in this paper : — (1) That our 
great schools and universities should give up treating Greek as a dead language, and should 
forthwith fling overboard their present fashion of pronouncing it in a barbarous and 
arbitrary fashion, which nobody understands but themselves ; (2) that considerations of 
policy, as well as of human sympathy, should induce all persons, whether inside or 
outside the University, to cultivate a living familiarity with the living inheritors of 
the noble Greek language ; and (3) that the Christian Churches, with whom Greek is 
not only an intellectual luxury, but a professional tool, should institute travelling scholar- 
ships for distinguished young theologians, for the purpose of getting in five months a 
living hold of the language of St Luke and St Paul, with more pleasure and profit than, 
under the present scholastic system of dead books and grammatical rules, can be achieved 
in as many years. 



( 115 ) 



VIII. — The Lower Carboniferous Volcanic Rocks of East Lothian [Garlton Hills). By 
Frederick H. Hatch, Ph.D., F.G.S., of the Geological Survey. Communicated by 
Sir Archibald Geikie, F.K.S. (With Two Plates.) 

(Read 2nd May 1892.) 

PAGE 

Introduction : Physical Features of the District, 115 

Part I. The Lower, Basic Lavas, 116 

„ II. The Upper, more Acid Lavas, 119 

„ III. The Materials Filling the Vents, 122 

Summary, 125 

Introduction: Physical Features of the District. 

The rich agricultural tract of country that forms the north-western part of East 
Lothian, undulating uniformly from the foot of the chain of the Lammermuirs towards 
the Firth of Forth, swells near Haddington into the cluster of the Garlton Hills, and the 
neighbouring masses of Traprain Law and North Berwick Law. 

The rocks that build up this elevated ground are lavas and tuffs that were produced 
during the period of volcanic activity that characterised the deposition of the Lower 
Carboniferous beds of Scotland. In East Lothian their eruption followed close on the 
deposition of the sandstones and marls that constitute the base of the calciferous sand- 
stone group.* 

Volcanic rocks of Lower Carboniferous age cover a considerable area in the Midland 
Valley of Scotland. Thus they form the ranges of the Campsie Hills and Kilpatrick, as 
well as the uplands of Renfrewshire and North Ayrshire. In all of these areas there is 
an intimate relationship of petrographical types. But in the Garlton Hills we meet with 
types not elsewhere developed. 

The stratigraphical relations of the rocks about to be described are somewhat obscured 
by the nature of the ground. The main features are given in Sir Archibald Geikie's 
classic paper on the " Carboniferous Volcanic Rocks of the Firth of Forth." t He 
estimates the thickness of the volcanic series between the red sandstones and the base of 
the Carboniferous Limestone at 1500 feet, though the estimate is stated to be only 
approximate on account of the paucity of sections. At the base of this thick pile lies a 
series of red and green tuffs, which can be well seen along the coast to the west of 
Dunbar, and on both sides of North Berwick. " After the cessation of the showers of 
ash and bombs, lava began to flow and continued to do so with little intermission until 

* A. Geikie, Trans. Boy. Soc. Edin., vol. xxix., 1880, p. 447. See also his Presidential Address to the Geological 
Society, 1892. t hoc. cit. 

VOL. XXXVII. PART I. (NO. 8). T 



116 DR HATCH ON THE LOWER CARBONIFEROUS 

the mass of the Garlton Hills had accumulated. No thick zones of tuff, nor interstrati- 
fied layers of sedimentary rock can anywhere he seen, separating the numerous lava beds, 
though it must be owned that the sections of the rocks are few and unsatisfactory." * 

The source of these streams of lava is indicated by the hills of Traprain Law and 
North Berwick, and the Bass Rock in the Firth of Forth. These are regarded as vents 
or "necks" by Sir Archibald Geikie. A microscopic examination shows that the 
material filling these vents is of similar character to that composing the flows. 

The lavas are divisible into two distinct series. Of these the lower consists of 
strongly basic rocks and forms a band extending from Traprain Law by Linton. White- 
kirk, and Balgone to Fenton Tower, while the upper is a more acid (trachytic) series. 
It forms the Garlton Hills and stretches away to the south between Whittingham and 
Linplum.t 



I. The Lower, Basic Lavas (Basalts). 

The basic rocks vary, from a type rich in olivine, and almost entirely free from 
felspar (limburgite), through ordinary olivine-basalts, to a more acid, strongly felspathic 
type (labradorite-basalt). In this series the percentages of silica and magnesia vary 
inversely. Thus the limburgite of Whitelaw Hill yields 40 per cent, of silica and 12 per 
cent, of magnesia; the olivine-basalt of Kippie Law, 46 per cent, of silica and 6 '8 per 
cent, of magnesia; the Hailes Castle rock, 49 per cent, of silica and 4*4 per cent, of 
magnesia; while the labradorite-basalt of Markle Quarry contains 49 '5 per cent, of silica 
and only 2 "8 per cent, of magnesia. 

The Limburgite of Whitelaw Hill. — Whitelaw Hill lies 4|- miles south-east of 
Haddington. The material examined was obtained from Chester's Quarry. It is composed 
of olivine, augite, and magnetic iron-ore.| Felspar is unrepresented, save by an occasional 
skeleton-crystal. The augite is of a pale claret colour, deepening to violet at the margin 
of the crystals. The olivine also is mainly unchanged in fresh specimens, but the course 
of the alteration is indicated by the presence of a bright green pleochroic substance, 
developed along the cleavage cracks. In more altered material the olivine is entirely 
replaced by the same chloritic substance. 

The larger crystals lie in a ground-mass, which consists chiefly of an aggregate of 
augite microlites, with intervening films and patches of a colourless glassy substance, 
which in places is powdered over with a yellowish dust.§ Slender needles of apatite are 

* A. Geikie, he. eit. 

t Survey Memoir on East Lothian, p. 47, and Sir A. Geikie's Presidential Address already cited. 

X The name limburgite was first applied by Rosenbusch to the rock of the Kaiserstuhl in Breisgau. Limburgites 
have since been described from numerous foreign localities, but are hitherto unrecorded in Great Britain. Quite 
recently I have been able to note the occurrence of a similar type among the basic rocks of the Carboniferous volcanic 
series in several places in Scotland besides that of Whitelaw Hill, e.g., Hill of Beath, Cowdenbeath (Fife) ; Pitandrew, 
Fardel Castle (Fife) ; Southdean Law, 7 miles south of Jedburgh. 

§ A similar appearance is described by BoitlCKY as characteristic for his " lichte Magmabasalt." 



VOLCANIC ROCKS OF EAST LOTHIAN. 



117 



occasionally seen, being conspicuous by reason of their great length ; and, here and there, 
scales of brown mica are present. In places the colourless " base " shows weak double 
refraction, and a close examination now and then discloses the presence of a six- or four- 
sided crystal of a colourless and pellucid mineral. The low index of refraction, shown by 
its faint outline and clear aspect, distinguishes it from apatite. Probably it is nepheline. 
The rock gelatinises readily with cold hydrochloric acid, and the jelly contains much 
soda, as shown by treatment with uranium acetate. Mr Player has been good enough 
to analyse a specimen of this rock, with the following result : — 



Silica, . 










40-2 


Titanic oxide, 










2-9 


Alumina, 










12-8 


Ferric oxide, 










4-0 


Ferrous oxide, 










10-4 


Lime, . 










10-4 


Magnesia, 










11-9 


Potash, . 










•8 


Soda, . 










27 


Loss by ignition 










3-4 



99-5 



Phosphoric acid is present. Sp. G. = 3 "03. 



The points brought out by this analysis are the low percentages of silica (40 per cent.), 
and alkalies (3*5 per cent., mostly soda), the high percentage of ferrous oxide (10'4 per 
cent.), magnesia (11 "9 per cent.), and lime (10 "4 per cent.), and the comparatively large 
amount of titanic acid (2*9 per cent.). The titanic acid appears to be mainly present in 
the augite, as the iron-ore, when isolated, proved to be magnetite and not ilmenite. 
Knop found 4 - 5 7 per cent, of titanic acid in the augite of the limburgite of the 
Kaiserstuhl in Breisgau. # 

The Olivine-Basalt of Kippie LawA — This is a dark compact rock, in which small 
glistening facets of felspar can be seen without the aid of a lens. The examination of a 
thin section under the microscope reveals the presence of porphyritic crystals of felspar 
and olivine, lying in a ground-mass composed of lath-shaped felspars, granular olivine 
and magnetite, and microlitic augite.| Olivine was originally the most abundant con- 
stituent, but that mineral has, during the processes of chemical change that make up the 
life-history of a rock, been converted into a fibrous aggregate of serpentine. With the 
serpentine limonite is associated, this mineral having been deposited along the boundary 
edges and in the cleavage cracks. 

The felspar is not abundant as a porphyritic constituent. It is a colourless and fresh 



* A. Knop, Zeitschrift fur Krystallographie, vol. x., 1885, p. 58. 

t No. 631 of the Survey Collection. 

I The Kippie Law type is occasionally found in other areas occupied by the Carboniferous volcanic rocks of 
Scotland. Thus it occurs south of Jedburgh, at Neides Law and Bonchester Hill, also in the Campsie Hills, 1| miles 
north of Lennoxtown. It is nearly allied to rocks of the Dalmeny type, which are abundantly distributed. It differs 
from these in the presence of porphyritic felspars. 



118 



DR HATCH ON THE LOWER CARBONIFEROUS 



variety of plagioclase — probably labradorite, for its high extinction angles, measured to 
the twin-striation, places it near the basic end of the lime-soda series. The larger crystals 
present the usual phenomena characterising the felspars of volcanic rocks — zonal extinc- 
tions between crossed nicols, and numerous inclusions (augite, magnetite, &c). The 
lath-shaped felspars of the ground-mass extinguish in too indefinite a manner to permit 
of the nature of the felspar being determined. A third stage in the genesis of the felspar 
is represented by the presence of small patches of a clear unstriped variety. Since there 
is no glassy base present, these felspar patches apparently resulted from the crystallisa- 
tion of the mother-liquor of the rock left in consolidation. 

With regard to structure, its most prominent feature is the more or less idiomorphic 
character of all the constituents. The porphyritic felspars occur in short rectangular 
prisms ; and the serpentinized olivine, in forms characteristic of that mineral. In the 
ground-mass the felspars have a long, lath-shaped habit ; olivine occurs in grains which 
in part are bounded by crystallographic contours ; and magnetite, in rectangular granules. 
Most pronounced of all, however, is the idiomorphic character of the microlitic augite. 
Viewed under a high power, the ground-mass is seen to be crowded with delicately- 
shaped prisms of augite, most of which are terminated at both ends by faces of the 
hemi-pyramid. 

In addition to the minerals already enumerated, apatite is present in fine needles, 
and there are a few patches of a bright green chlorite, with which brown mica is 
occasionally associated. 

The inter-relations of the various constituents indicate that they were probably 
formed in the following order: — iron-ore and apatite, olivine, augite, plagioclase, and 
finally, the unstriped felspar occurring in patches in the ground-mass. 

The rock was analysed some years ago for the Geological Survey by Mr J. S. Grant- 
Wilson : — 



Si0 2 . 












4601 


A1 2 3 - 












19-19 


Fe 2 3 - 












591 


FeO . 












6-75 


MnO . 












19 


CaO . 












8-68 


MgO . 












6-81 


K 2 . 












1-20 


Na 2 . 












3-27 


H 2 . 












3-07 




101-08 






Sp. gr 


avity = S 


•8. 







The Olivine-Basalt of Hailes Castle* — This rock has a more felspathic character. 
It consists chiefly of felspar microlites and slender laths, with granules of augite and 
particles of magnetite. In this ground-mass lie isolated limonitic pseudomorphs after 
olivine, and a few glomero-porphyritic crystals of striped felspar. A basalt occurring at 

* No. 630 of the Survey Collection. 



VOLCANIC ROCKS OF EAST LOTHIAN. 



119 



Blackie Heughs is similar to that of Hailes Castle, in the character of its ground-mass, 
but it differs from that rock by the absence of porphyritic crystals of felspar. On the 
other hand, there is a greater amount of olivine crystals, with which some porphyritic 
grains of augite are associated. 

The chemical composition of the Hailes Castle rock is represented in the following 
analysis, made for the Geological Survey by Mr J. S. Grant- Wilson : — 



Si0 2 . 












49-07 


A1 2 3 . 




. 






19-43 


Fe 2 3 . 










10-58 


FeO . 












2-35 


MnO . 












•32 


CaO. . 












7-87 


MgO . 












4-36 


K 2 . 












■98 


Na 2 . 












331 


H 2 . 












2-26 




100-53 






Sp. 


G. 276 









The " Ldbradorite- Basalt " of Markle Quarry* — This is a still more felspathic 
type. In this rock olivine only occurs in small sporadic grains, while plagioclase felspar 
is present in numerous large porphyritic crystals lying in a ground-mass of laths, 
microlites, and granules of felspar, together with dispersed magnetite and probably 
augite, the latter mineral being obscured by a ferruginous product of decay. 

This rock, which must be classed as a felspathic basalt ("labradorite"), has also been 
analysed by Mr Wilson with the following result : — 



Si0 2 . 












49-54 


A1 2 3 . 












22-23 


Fe 2 3 . 












9-55 


FeO . 
MnO . 












112 

•08 


CaO . 












719 


MgO . 












2-80 


K 2 . 












1-81 


Na 2 . 












4-56 


H 2 . 












2.42 



10130 



Sp. G. 2-7. 



II. The Upper, more Acid Lavas (Trachytes). 

The Porphyritic Trachytes are compact rocks of pale grey, buff, and brown colours, 
and are chiefly characterised by the presence of clear glancing crystals of unstriped 
felspar. These crystals vary considerably in the different flows, both in regard to size 
and abundance. They are largest and most plentifully developed in the rock quarried 
at Peppercraig, close to the town of Haddington. This rock consists of clear felspar 
crystals, sometimes as much as 10 mm. in length, and a dark microcrystalline ground- 

* No. 629 of the Survey Collection. 



120 DR HATCH ON THE LOWER CARBONIFEROUS 

mass in about equal proportions. On the other hand, the rock on which the Hopetoun 
Monument stands has an almost flinty texture with few and small felspars. 

With respect to chemical composition, these rocks contain from 60 to 63 per cent, of 
silica. The alkalies generally amount to about 10 per cent., but in some cases are 
lower. The magnesia is always less than 1 per cent., while the lime varies from 2 to 3 
per cent. The ratio between potash and soda is not the same for all the types. Thus 
in the Peppercraig rock the soda is slightly in excess of the potash, while in a specimen 
from Kae Heughs the reverse is the case. The chemical composition of the Garlton 
trachytes is thus in accord with that of well-known trachytes from other areas.* 

Examined under the microscope, these sections show that the rocks are composed of 
large and remarkably limpid felspar crystals, imbedded in a minutely crystalline ground- 
mass. The latter consists chiefly of felspar, but also contains granules of augite and 
particles of magnetite. None of the rocks contain any interstitial glassy matter ; for 
under a high power the ground-mass is invariably found to be completely crystalline. 
One of the most striking points about these rocks is the decided separation of the por- 
phyritic felspar from the microlitic felspar of the ground-mass. In no case could any 
gradation or passage between the two generations be made out. There is no doubt that 
we have here an instance of the crystallization of one constituent of the same rock-magma 
under widely separated conditions. The porphyritic felspars represent the intra-telluric 
conditions, that is to say, they were developed while the imprisoned magma simmered 
below, prior to its escape upwards. On eruption, the cooling was quick enough to pro- 
duce a uniform and even-grained ground-mass, but not sufficiently rapid to permit of any 
of the magma consolidating as glass. As further evidence in favour of this view, attention 
is directed to the remarkable zones of fresh felspar deposited round fragments of intra- 
telluric felspars broken on eruption. 

Nature of the Felspar. — With the exception of isolated occurrences, the great 
majority of the rocks contain porphyritic crystals of sanidine, showing the rectangular 
form, Carlsbad twinning, and clear glassy habit characteristic of that mineral. A 
cleavage flake (parallel to the face M) gave an extinction angle of 6-7°, measured to the 
edge P.M. In many of the sections examined the crystals are as clear and unaltered as 
in the most modern trachytes. Since the rocks are of Carboniferous age, this shows a 
most remarkable resistance to the disintegrating action of the weather. 

Inclusions of augite, magnetite, &c, are abundant. These are often of a globular 
character, and are irregularly scattered through the crystals or arranged in marginal 
zones. The large amount of included matter occurring in marginal zones suggests that 
a considerable portion was taken up during the continued growth of the crystals. 

The lath-shaped microlites and granules that make up the ground-mass also consist 
of a clear glassy felspar, apparently of the same nature as the porphyritic sanidine. 

Although in most of the rocks the whole of the porphyritic felspar is orthoclastic, in 

* The Puy de Dome trachyte has Si0 2 , 62-83 ; K 2 0, 8"88 ; Na 2 0, 5-03— one of the Ehon trachytes ; Si0 2 , 63-40 ; 
K 2 0, 3-54 ; Na 2 0, 8-39 (Kalkowsky)— trachyte from Monte dell' Imperatore, Italy ; Si0 2) 61-05; K 2 0, 5-28 ; Na 2 0, 
5-94— trachyte from Monte Vettia ; Si0 2) 6187 ; K 2 0, 6-51 ; Na^, 5-07.— (J. Roth.) 



VOLCANIC ROCKS OF EAST LOTHIAN. 121 

some a striped felspar is also developed (Phantassie Quarry, Skid Hill, Bangley Quarry). 
In the Bangley Quarry so much plagioclase is present as to suggest a passage to the 
andesites. The chemical analysis points the same way, the silica percentage being only 
58*5. (See Chemical Analyses of the trachytes.) 

Structure of the Trachytes. — The noncrystalline character of the ground-mass, and 
the wide breach between its constituent microlites and the porphyritic sanidine crystals, 
have already been alluded to. One interesting feature in regard to the porphyritic 
crystals remains to be noticed. There is, namely, a tendency in the latter to pack 
themselves together, producing a glomero-porphyritic structure. This is especially 
evident in the rocks of Kae Heughs, Dirlton Craig, and Peppercraig. The crystals are 
so closely fused that the composite character of the glomero-porphyritic aggregates is only 
noticeable between crossed nicols. The component grains then become distinct in con- 
sequence of their different action on polarised light. One such mass, that appeared 
homogeneous in ordinary light, was found to be made up of fifteen distinct grains when 
examined between crossed nicols. In some cases the grains are allotriomorphic towards 
the interior of the mass, but present idiomorphic contours at the exterior. The same 
phenomenon has been observed by Mr Teall in the glomero-porphyritic felspar of the 
Tynemouth Dyke. # 

With regard to the ground-mass, a beautiful micro-fluidal structure is produced in 
many of the rocks {e.g., Dirlton Craig and Skid Hill) by the orientation of the microlitic 
felspars of the ground-mass in lines which flow and eddy round the porphyritic crystals. 
The interstices between the lath-shaped felspars are filled with allotriomorphic felspar and 
with granules of augite : in no case was any glassy or felsitic base observed. Larger and 
in some cases well-contoured crystals of a greenish augite sometimes occur. They usually 
contain much enclosed magnetite. 

The Non-Porphyritic Trachytes. — Non-porphyritic varieties of the trachytes occur at 
Score Hill, Lock Pit Hill, Craigie Hill, and Pencraig. They are pale rocks, tinted 
variously with buff, pink, mauve, and cream colours. In texture they are compact and 
" trachytic," and present a somewhat glistening appearance when subjected to minute 
inspection. Examined under the microscope, they are seen to consist of a mass of close 
interlacing lath-shaped crystals of a felspar which, between crossed nicols, gives no sign 
of twin-striation. Scattered evenly through the sections are small patches of powdery 
carbonate (calcite or dolomite), in some cases apparently pseudomorphous after augite. 
Under a higher power the structure is seen to be completely, though minutely, crystalline, 
the interspaces between the lath-shaped felspars being filled with granules of the same 
mineral. Iron-ores are present in small quantity. A fluidal structure is occasionally 
indicated by a parallel arrangement of the felspar microlites. 

In the salmon-pink rock of Lock Pit Hill the microlitic and long lath-shaped character 
of the felspars is strongly pronounced, slender crystals of orthoclase, lying in a ground- 

* Some North of England Dykes, Quart. Journ. Geol. Soc, 1884, p. 234. 



122 



DR HATCH ON THE LOWER CARBONIFEROUS 



mass of minute spicular microlites of the same mineral ; but in other rocks (e.g., Pencraig 

Quarry *) there is less tendency to develop lath-shaped crystals, the granular form taking 

its place. In others, again (e.g., at Craigie Hill), a passage to the porphyritic trachytes 

is produced by the sporadic appearance of sanidine crystals belonging to an earlier 

generation. 

Chemical Analyses of the Trachytes.^ 





Peppercraig, 

Sect. No. 615 

(Wilson). 


Hopetoun 
Monument, * 
Sect. No. 620 
(G. Barrow). 


Kae Heughs, 

Sect. No. 635 

(Wilson). 


Phantassie,* 
Sect. No. 622 
(A. Dick, jun.). 


Bangley 

Quarry, * 

Sect. No. 625 

(A.Dick,jun.). 


Si0 2 
A1 2 3 
Fe 2 3 
FeO 
MnO 
CaO 
MgO 
K 2 
H 2 
Loss on igni- > 
tion J 


62-61 

18-17 

0-32 

4-25 

•21 

2-58 

•74 

4-02 

6-49 

•80 


62-50 
18-51 

| 4-39 

2-00 

•61 

6-31 

3-44 

2-10 


61-35 

16-88 

•41 

5-01 

•26 

2-39 

•44 

6-12 

5-26 

1-70 


59-50 

18-25 

4-81 

2-34 

2-10 

•70 

6-30 

5-03 

1-60 


58-50 

21-12 

4-68 

370 
•93 

5-84 
3-90 

2-00 




10019 


99-86 


99'82 


100-63 


100-67 


Sp. G. 


2-6 


... 


2-6 







III. The Volcanic Vents. 

The position of the vents, from which the lavas of the Garlton Hills took their source, 
is indicated by the presence, on the margin of the volcanic area, of masses of agglomerate 
and plugs of igneous rock. Some of these are exposed along the coast of the Firth of 
Forth, between Dunbar and North Berwick ; others form good-sized hills, such as North 
Berwick Law (612 ft.), on the north of the district, and Traprain Law (724 ft.), on the 
south. The Bass Rock (350 ft.) marks the site of another " neck." 

A portion of the earliest (basic) lavas doubtless flowed from vents situated near 
Dunbar. Thus the knob of olivine-basalt on which Dunbar Castle stands, is probably the 
exposed core of one of the pipes of emission. This rock proves to be very basic, being 
composed of numerous porphyritic crystals of olivine, imbedded in a brown crypto- 
crystalline ground-mass, containing grains of augite, but not much felspar. Again, a 
limburgite, very similar to that which forms Whitelaw Hill, occurs as an intrusive mass 
in tuff at Gin Head, Tantallon. 

* Figured by Sir Archibald Geikie, loc. cit. 

t These analyses were kindly made for me by Messrs G. Barrow and A. Dick, jun., in the Laboratory of the 
Geological Survey at 28 Jermyn Street, London. 



VOLCANIC ROCKS OF EAST LOTHIAN. 



123 



Trachytic material builds up the plugs that form the Bass Eock and North Berwick 
Law, while Traprain Law consists of an interesting trachytic phoDolite,* a type of rock 
which does not appear to be represented elsewhere in the district, although it belongs to 
the same petrographical family as the sanidine-trachytes of the Garltons. 

North Berwick Law.f — This shapely hill, which forms a prominent feature in the 
scenery near North Berwick, is built up of a reddish brown rock of close texture, and 
characterised by a curious glistening appearance. The microscope shows it to be a 
trachyte. It is composed of a plexus of long and slender lath-shaped crystals of clear 
felspar (sanidine), occasionally twinned on the Carlsbad type. The meshes between the 
longer crystals are filled with a confused mass of minute spicules and microlites of the 
same mineral. Beyond an indefinite ferruginous material, felspar is the only constituent 
visible in the slide. 

The rock has been analysed by Mr J. S. Grant-Wilson for the Geological Survey of 
Scotland, with the following result : — 



Si0 2 . 










60-15 


A1 2 B 


. 








18-04 


Fe 2 3 










4-44 


FeO . 


. 








1-82 


MnO . 










•13 


CaO . 










1-68 


MgO . 


. 








•98 


K 2 . 










4-15 


Na 2 . 










607 


H 2 . 










2-06 




99-52 




Sp. ( 


>. = 2-4€ 









It will be seen from this analysis that the composition of the rock is in close agree- 
ment with the trachyte-flows (compare the analysis of the Peppercraig rock). In 
petrographical habit it resembles some of the non-porphyritic trachytes of the district. 

The Bass Eock. — It was suggested by Sir Archibald Geikie that the Bass Rock was 
one of the vents from which flowed the lavas of the Garlton Hills. I have been able to 
substantiate the correctness of the suggestion by a petrographical study of material 
obtained by Mr J. G. Goodchild during a recent visit to the island. The rock proves to 
be a trachyte, similar in character to that of North Berwick Law, and to the non- 
porphyritic division of the trachytic flows. The reddish-brown material is composed 
almost exclusively of felspar (sanidine), the rectangular facets of which can be easily 

* The only phonolite that has hitherto been described in the British Isles is that of the Wolf Eock, off the coast 
of Cornwall. 

t In the Survey Memoir on East Lothian (p. 51), North Berwick Law is described as "a round or slightly oval 
plug of felstone, which comes up vertically through the ash, and when it reaches the surface of the ground tapers up 
into a cone, of which the top is 612 feet above the sea. The rock on the higher part of the hill is a compact and finely 
crystalline clinkstone, while further down it becomes more loose and granular in texture. At the foot of the cone, on 
the west side, sandstone and black shale (strata, probably in the ashy series) are seen to dip away from the felstone at 
an angle of 30°." 

VOL. XXXVII. PART I. (NO. 8). U 



124 



DR HATCH ON THE LOWER CARBONIFEROUS 



distinguished with the lens, when the hand-specimen is held in a good light. A slice 
examined under the microscope is seen to be made up of rather broad lath-shaped 
crystals, colourless, of glassy habit, and showing no twin-striation between crossed nicols. 
The crystals are either single individuals or dual twins built up on the Carlsbad type. 
When not in juxtaposition, the intervening spaces between the lath-shaped crystals are 
filled with microlitic felspar. No ferro-magnesian mineral was observed, but there is a 
good deal of dusty ferruginous material present. 

Mr G. Barrow, of the Geological Survey, has kindly analysed this rock for me in 
the Survey Laboratory at Jermyn Street : — 



Si0 2 .... 


57-50 


A1 2 3 .... 


18-89 


Fe 2 3 ) 
FeO | 


7-51 


CaO 


1-80 


MgO .... 


1-33 


K 2 .... 


5-90 


Na 2 


5-71 


Loss on ignition 


1-70 



100-34 

Traprain Law. — This hill, which rises out of white sandstones and shales on the 
southern margin of the volcanic area, is built up of a close-grained, dark-brown to grey 
rock, occasionally presenting glancing cleavage surfaces of a clear, glassy felspar (sanidine). 
Fresh-fractured surfaces have the glistening or greasy lustre already noticed in the 
trachytes of North Berwick Law and the Bass Eock. Some varieties are speckled over 
with dark spots, while others show a distinct banded (flow) structure, especially visible 
in the stone quarried at Black Cove. A tendency to split into rather thin plates is also 
noticeable. Under the hammer the stone has a remarkable sonorous ring, and small 
fragments rattled together give a metallic clink.* 

Microscopic examination shows that the rock consists mainly of small lath-shaped 
crystals of sanidine, arranged so as to produce a marked micro-fluidal structure. 
Porphyritic crystals are rare, but occasionally occur. 

A bright green pyroxene is distributed through the rock in small crystals and 
ophitic patches. It shows allotriomorphic relations with regard to the felspar. That 
this mineral is a soda-augite is proved conclusively by the chemical analysis, there being 
practically no magnesia present. In the few cases, however, where extinction-angles 
could be measured to definite boundaries, they proved too high for segirine ; but the 
presence of this mineral cannot be considered to be thereby excluded, as the association 
of segirine with a soda-augite of similar appearance, but high extinction-angles, has been 
recorded. 

A small quantity of iron-ore and of apatite occurs in isolated granules. 

* This property, which appears to be a characteristic of the phonolites, was noticed in the Survey Memoir (p. 52), 
where the rock of Traprain Law is described as a " felstone (clinkstone)." 



VOLCANIC ROCKS OF EAST LOTHIAN. 



125 



Certain parts of the sections are dusted over with a brown powdery material. A near 
examination of these portions discloses in them the presence of small colourless patches 
which, when rotated between crossed nicols, remain nearly or quite dark. These small 
patches consist of nepheline, or of zeolitic products of its decomposition ; but only a close 
examination of very thin sections enables one to detect the presence of occasional six- and 
four-sided crystal-contours.* The mineral, however, has been very largely converted into 
the zeolites, analcime, and natrolite, of which there is abundant evidence in the sections. 
With regard to micro-chemical tests, a drop of hydrochloric acid placed upon a smooth 
surface of the rock rapidly produces gelatinisation ; and the jelly, dried and treated with 
acetate of uranium, develops abundant and characteristic crystals of uranate of sodium. 
The distribution of the nepheline, and its zeolitic products of decomposition, is well 
shown by treatment with hydrochloric acid, and subsequent staining with fuchsine. 

Mr Player has kindly analysed the rock for me, and his results are the following : — 

Analysis of Phonolite (Sect. No. 4526). 



Silica, 










56-8 


Titanic acid, 










•5 


Alumina, 










19-7 


Ferric oxide, 










2-2 


Ferrous oxide, . 










35 


Manganous oxide, 










•2 


Lime, . 










2-2 


Magnesia, 










•4 


Soda, . 










43 


Potash, 










7-1 


Loss by ignition, 










2-5 




99-4 




Sp. G 


= 2-588 









The small amount of magnesia ("4 per cent.), and the high percentage of alkalies (1T4 
per cent), are interesting points brought out by this analysis. 



Summary. 

The Carboniferous volcanic rocks of East Lothian (the Garlton Hills, &c.) consist of 

(1) A lower, basic series, comprising felspar-free basalts, rich in olivine and augite, 
and containing much glassy matter with occasional crystals of nepheline (limburgite of 
Whitelaw Hill) ; normal olivine-basalts (e.g., Kippie Law and Hailes Castle) ; and a very 
felspathic type (labradorite-basalt of Markle Quarry). 

(2) An upper, trachytic series, which builds the main portion of the Garlton Hills, 
comprising trachytes with porphyritic sanidine (e.g., Peppercraig, Kae Heughs, and 

* The low index of refraction, and the absence of a needle-form, serve as a distinction from apatite. Professor 
Rosenbusch of Heidelberg, to whom I submitted specimens, confirms the identification of the nepheline, and refers the 
rock to the trachytic phonolites of his classification. 



120 



LOWER CARBONIFEROUS VOLCANIC ROCKS OF EAST LOTHIAN. 



Hopetoun Monument) ; trachytes with porphyritic sanidine and plagioclase {e.g., 
Phantassie Quarry, Skid Hill, and Bangley Quarry), and non-porphyritic trachytes (e.g., 
Score Hill, Lock Pit Hill, Craigie Hill, and Pencraig). 

(3) The material filling the volcanic vents, comprising basic rocks (olivine-basalts 
and limburgites), at Dunbar and Tantallon ; trachytes, at North Berwick Law and the 
Bass Rock ; and a phonolite, at Traprain Law. 



EXPLANATION OF THE FIGURES. 



Plate I. 



Fig. 1. Limburgite of Whitelcav Hill, composed of olivine, augite, magnetite, and glassy matter. In 
ordinary light. 

Fig. 2. Labradorite- Basalt of Jharkle Quarry, Garlton Hills, composed of porphyritic crystals of striped 
labradorite and olivine in a microlitic ground-mass with granules of magnetite. Between crossed nicols. 

Fig. 3. Trachyte of the Bass Rock, composed of lath-shaped crystals of sanidine. Between crossed 
nicols. 

Fig. 4. Trachyte of North Berwick Law, composed of lath-shaped crystals and microlites of sanidine. 
Between crossed nicols. 

Plate II. 



Fig. 1. Phonolite of Traprain Law, composed of sanidine, nepheline, and green soda-augite. In ordinary 
light. 

Fig. 2. Sanidine-Trachyte of Peppercraig, near Haddington, composed of sanidine and augite in a 
microlitic (felspathic) ground-mass of glomero-porphyritic structure. Between crossed nicols. 



Trans. Roy. Soc. Edm r , Vol. XXXVII. 
D P F.H. Hatch on the Petrography of the Rocks of the Garlton Hills. 




M e Farla.ne fcErs^ine, LitV;? Edii 



( 127 ) 



IX. — On the Glacial Succession in Europe. By Professor James Geikie, 
D.C.L., LL.D., F.K.S., &c. (With a Map.) 

(Read 16th May 1892.) 

For many years geologists have recognised the occurrence of at least two boulder- 
clays in the British Islands and the corresponding latitudes of the Continent. It is no 
longer doubted that these are the products of two separate and distinct glacial epochs. 
This has been demonstrated by the appearance of intercalated deposits of terrestrial, 
freshwater, or, as the case may be, marine origin. Such interglacial accumulations 
have been met with again and again in Britain, and they have likewise been detected at 
many places on the Continent, between the border of the North Sea and the heart of 
Kussia. Their organic contents indicate in some cases cold climatic conditions ; in others, 
they imply a climate not less temperate or even more genial than that which now 
obtains in the regions where they occur. Nor are such interglacial beds confined to 
northern and north-western Europe. In the Alpine Lands of the central and southern 
regions of our Continent they are equally well developed. Impressed by the growing 
strength of the evidence, it is no wonder that geologists, after a season of doubt, should 
at last agree in the conclusion that the glacial conditions of the Pleistocene period were 
interrupted by at least one protracted interglacial epoch. Not a few observers go 
further, and maintain that the evidence indicates more than this. They hold that three 
or even more glacial epochs supervened in Pleistocene times. This is the conclusion I 
reached many years ago, and I now purpose reviewing the evidence which has accumu- 
lated since then, in order to show how far it goes to support that conclusion. 

In our islands we have, as already remarked, two boulder-clays, of which the lower 
or oldest has the widest extension southwards, for it has been traced as far as the valley 
of the Thames. The upper boulder-clay, on the other hand, does not extend south of 
the Midlands of England. In the north of England, and throughout Scotland and the 
major portion of Ireland, it is this upper boulder-clay which usually shows at the surface. 
> The two clays, however, frequently occur together, and are exposed again and again in 
deep artificial and natural sections, as in pits, railway-cuttings, quarries, river-banks, and 
sea-clifls. Sometimes the upper rests directly upon the lower ; at other times they are 
separated by alluvial and peaty accumulations or by marine deposits. The wider 
distribution of the lower till, the direction of transport of its included erratics, and the 
trend of the underlying roches moutonnees and rock-striae, clearly show that the earlier 
mer de glace covered a wider area than its successor, and was confluent on the floor of 
the North Sea with the Scandinavian ice-sheet. It was during the formation of the 
lower till, in short, that glaciation in these islands attained its maximum development. 

VOL. XXXVII. PART I. (NO. 9). X 



128 PROFESSOR JAMES GEIKIE ON THE 

The interglacial beds, which in many places separate the lower from the upper till, 
show that after the retreat of the earlier mer de glace the climate became progressively 
more temperate, until eventually the country was clothed with a flora essentially the 
same as the present. Wild oxen, the great Irish deer, and the horse, elephant, rhinoceros, 
and other mammals then lived in Britain. From the presence of such a flora and fauna 
we may reasonably infer that the climate during the climax of interglacial times was as 
genial as now. The occurrence of marine deposits associated with some of the inter- 
glacial peaty beds shows that eventually submergence ensued ; and as the shells in some 
of the marine beds are boreal and Arctic forms, they prove that cold climatic conditions 
accompanied the depression of the land. To what extent the land sank under water we 
cannot tell. It may have been 500 feet or not so much, for the evidence is somewhat 
unsatisfactory. 

The upper boulder-clay of our islands is the product of another mer de glace, which 
in Scotland would seem to have been hardly less thick and extensive than its predecessor. 
Like the latter, it covered the whole country, overflowed the Outer Hebrides, and became 
confluent with the Scandinavian inland ice on the bed of the North Sea. But it did not 
flow so far to the south as the earlier ice-sheet. 

It is well known that this later mer de glace was succeeded in our mountain regions 
by a series of large local glaciers, which geologists generally believe were its direct 
descendants. It is supposed, in short, that the inland ice, after retreating from the low 
grounds, persisted for a time in the form of local glaciers in mountain valleys. This 
view I also formerly held, although there were certain appearances which seemed to 
indicate that, after the ice-sheet had melted away from the lowlands and shrunk far into 
the mountains, a general advance of great valley-glaciers had taken place. I had 
observed, for example, that the upper boulder-clay is often well developed in the lower 
reaches of our mountain valleys — that, in fact, it may be met with more or less 
abundantly up to the point at which large terminal moraines are encountered. More 
than this, I had noticed that upland valleys, in which no local or terminal moraines 
occur, are usually clothed and paved with boulder-clay throughout. Again, the aspect 
of valleys which have been occupied by large local glaciers is very suggestive. Above 
the point at which terminal moraines occur only meagre patches of till are met with on 
the bottoms of the valleys. The adjacent hill-slopes up to a certain line may show bare 
rock, sprinkled perchance with erratics and superficial morainic detritus ; but above this 
line, if the acclivity be not too great, boulder-clay often comes on again. These appear- 
ances are most conspicuously displayed in the Southern Uplands of Scotland, particularly 
in South Ayrshire and Galloway, and long ago led me to suspect that the local glaciers 
into which our latest mer de glace was resolved, after retreating continuously towards 
the heads of their valleys, so as to leave the boulder-clay in a comparatively unmodified 
condition, had again advanced and ploughed this out, down to the point at which they 
dropped their terminal moraines. Subsequent observations in the Highlands and the Inner 
and Outer Hebrides confirmed me in my suspicion, for in all those regions we meet with 



GLACIAL SUCCESSION IN EUROPE. 129 

phenomena of precisely the same kind. My friends and colleagues, Messrs Peach and 
Horne, had independently come to a similar conclusion ; and the more recent work of the 
Geological Survey in the North- West Highlands, as they inform me, has demonstrated 
that after the dissolution of the general ice-sheet, underneath which the upper boulder- 
clay was accumulated, a strong recrudescence of glacial conditions supervened, and a 
general advance of great valley-glaciers took place — the glaciers in many places coalescing 
upon the low grounds to form united mers de glace of considerable extent. 

The development of these large glaciers, therefore, forms a distinct stage in the 
history of the Glacial Period. They were of sufficient extent to occupy all the fiords of 
the Northern and Western Highlands, at the mouths of which they calved their icebergs, 
and they descended the valleys on the eastern slopes of the land into the region of the 
great lakes, at the lower ends of which we encounter their outermost terminal moraines. 
The Shetland and Orkney Islands and the Inner and Outer Hebrides at the same time 
nourished local glaciers, not a few of which flowed into the sea. Such, for example, was 
the case in Skye, Harris, South Uist, and Arran. The broad Uplands of the south were 
likewise clothed with snow-fields that fed numerous glaciers. These were especially 
conspicuous in the wilds of Galloway, but they appeared likewise in the Peeblesshire 
hills ; and even in less elevated tracts they have left more or less well-marked traces of 
their former presence. 

It is to this third epoch of glaciation that I would assign the final scooping out of 
our lake-basins and the completion of the deep depressions in the beds of our Highland 
fiords. All the evidence, indeed, leads to the conviction that the epoch was one of long 
duration. 

It goes without saying that what holds good for Scotland must, within certain limits, 
hold good also for Ireland and England. In Wales and the Cumberland Lake District, 
and in the mountain regions of the sister island, we meet with evidence of similar 
conditions. Each of those areas has obviously experienced intense local glaciation sub- 
sequent to the disappearance of the last big ice-sheet. 

Attention must now be directed to another series of facts, which help us to realise 
the general conditions that obtained during the epoch of local glaciation. In the basin of 
the estuary of the Clyde, and at various other places both on the west and east coasts of 
Scotland, occur certain clays and sands, which overlie the upper boulder-clay, and in some 
places are found wrapping round the kames and osar of the last great ice-sheet. These 
beds are charged with the relics of a boreal and Arctic fauna, and indicate a submergence 
of rather more than 100 feet. In the lower reaches of the rivers Clyde, Forth, and Tay 
the clays and sands form a well-marked terrace, and a raised sea-beach, containing similar 
organisms, occurs here and there on the sea-coast, as between Dundee and Arbroath, on 
the southern shores of the Moray Firth, and elsewhere. When the terraces are traced 
inland they are found to pass into high-level fluviatile gravels, which may be followed 
into the mountain valleys, until eventually they shade off into fluvio-glacial detritus 
associated with the terminal moraines of the great local glaciers. It is obvious, in short, 



130 PROFESSOR JAMES GEIKIE ON THE 

that the epoch of local ice-sheets and large valley-glaciers was one also of partial sub- 
mergence. This is further shown by the fact that in some places the glaciers that 
reached the sea threw down their moraines on the 100-feet beach. It must have been 
an epoch of much floating ice, as the marine deposits contain now and again many 
erratics, large and small, and are, moreover, frequently disturbed and contorted as if 
from the grounding of pack-ice. 

The phenomena which I have thus briefly sketched suffice to show that the epoch 
of local glaciation is to be clearly distinguished from that of the latest general mer de 
glace. I have long suspected, indeed, that the two may have been separated by as wide 
an interval of time as that which divided the earlier from the later epoch of general glacia- 
tion. Again and again I have searched underneath the terminal moraines, in the faint hope 
of detecting interglacial accumulations. My failure to discover these, however, did not 
weaken my conviction, for it was only by the merest chance that interglacial beds could 
ever have been preserved in such places. I feel sure, however, that they must occur 
among the older alluvia of our Lowlands. Indeed, as I shall point out in the sequel, it is 
highly probable that they are already known, and that we have hitherto failed to recog- 
nise their true position in the glacial series. 

Although we have no direct evidence to prove that a long interglacial epoch of mild 
conditions immediately preceded the advent of our local ice-sheets and large valley-glaciers, 
yet the indirect evidence is so strong that we seem driven to admit that such must 
have been the case. To show this I must briefly recapitulate what is now known as to 
the glacial succession on the Continent. It has been ascertained, then, that the Scandi- 
navian ice has invaded the low grounds of Germany on two separate occasions, which 
are spoken of by continental geologists as the " first " and " second " glacial epochs. 
The earlier of these was the epoch of maximum glaciation, when the inland ice flowed south 
into Saxony, and overspread a vast area between the borders of the North Sea and the 
base of the Ural Mountains. This ice-sheet unquestionably coalesced with the mer de 
glace of the British Islands. Its bottom-moraine and associated fluvio-glacial detritus are 
known in Germany as lower diluvium, and the various phenomena connected with it 
clearly show that the inland ice radiated outwards from the high grounds of Scandinavia. 
The terminal front of that vast mer de glace is roughly indicated by a line drawn from 
the south coast of Belgium round the north base of the Harz, and by Leipzig and Dres- 
den to Krakow, thence north-east to Nijni Novgorod, and further north to the head- 
waters of the Dvina and the shores of the Arctic Sea near the Tcheskaia Gulf. 

The "lower diluvium" is covered in certain places by interglacial deposits and an 
overlying " upper diluvium " — a succession clearly indicative of climatic changes. In the 
interglacial beds occur remains of Elephas antiquus and other Pleistocene mammals, and 
a flora which denotes a genial temperate climate. One of the latest discoveries of inter- 
glacial remains is that of two peat-beds lying between the lower and upper diluvium 
near Griinenthal in Holstein.* Among the abundant plant-relics are pines and firs (no 

* Neues Jahrbuchf. Min. Geol. u. Palceont. ? 1891, ii. pp. 62, 228; Ibid., 1892, i. p. 114. 



GLACIAL SUCCESSION IN EUROPE. 131 

longer indigenous to Schleswig-Holstein) aspen, willow, white birch, hazel, hornbeam, 
oak, and juniper. Associated with these are Ilex and Trapa natans, the presence of 
which, as Dr Weber remarks, betokens a climate like that of western Middle Germany. 
Amongst the plants is a water-lily, which occurs also in the interglacial beds of Switzer- 
land, but is not now found in Europe. The evidence furnished by this and other inter- 
glacial deposits in North Germany shows that, after the ice-sheet of the lower diluvium 
had melted away, the climate became as temperate as that which is now experienced in 
Europe. Another recent find of the same kind is the "diluvial" peat, &c, of Klinge 
in Brandenburg, described by Professor Nehring.* These beds have yielded remains of 
elk (Cervus alces), rhinoceros (species not determined), a small fox (?), and megaceros. 
This latter is not the typical great Irish deer, but a variety (C. megaceros, var. Ruffii, 
Nehring). The plant-remains include pine, fir {Picea excelsa), hornbeam, warty birch 
(Betula verrucosa), various willows (Salix repens, S. aurita, S. caprea ? S. cinerea), 
hazel, poplar (?), common holly, &c. It is worthy of note that here also the interglacial 
water-lily (Cratopleura helvetica) of Schleswig-Holstein and Switzerland makes its 
appearance. Dr Weber writes me that the facies of this flora implies a well-marked 
temperate insular climate (Seeklima). The occurrence of holly in the heart of the 
Continent, where it no longer grows wild, is particularly noteworthy. The evidence 
furnished by such a flora leads one to conclude that at the climax of the genial inter- 
glacial epoch, the Scandinavian snowfields and glaciers were not more extensive than 
they are at present. 

The presence of the upper diluvium, however, proves that such genial conditions 
eventually passed away, and that an ice-sheet again invaded North Germany. But this 
later invasion was not on the same scale as that of the preceding one. The geographical 
distribution of the upper diluvium and the position of large terminal moraines put this 
quite beyond doubt. The boulder-clay in question spreads over the Baltic provinces of 
Germany, extending south as far as Berlin, and west into Schleswig-Holstein and Den- 
mark. At the climax of this later cold epoch glaciers occupied all the fiords of Norway, 
but did not advance beyond the general coast-line. Norway, at that time, must have 
greatly resembled Greenland — the inland ice covering the interior of the country, and 
sending seawards large glaciers that calved their icebergs at the mouths of the great 
fiords. In the extreme south, however, the glaciers did not quite reach the sea, but piled 
up large terminal moraines on the coast-lands, which may be followed thence into Sweden 
in an easterly direction by the lower end of Lake Wener and through Lake Wetter. A 
similar belt of moraines marks out the southern termination of the ice-sheet in Finland. 
Between Sweden and Finland lies the basin of the Baltic, which, at the epoch in ques- 
tion, was filled with ice, forming a great Baltic glacier. This glacier overflowed the 
Aland Islands, Gottland, and Oland, fanning out as it passed towards the south-west and 

* Naturvrissenschaftliche Woclienschrift, Bd. vii. (1892), No. 4, p. 31. The plants were determined by Dr Weber, 
Professor Wittmack, and Herr Warnstorf. [More recent investigations have considerably increased our knowledge of 
this flora. See Naturwissenschaftliche Wochenschrift, Bd. vii. (1892), Nr. 24, 25. Ausland, 1892, Nr. 20.] 



132 PROFESSOR JAMES GEIKIE ON THE 

west, so as to invade on the south the Baltic provinces of Germany, while in the north 
it traversed the southern part of Scania and overwhelmed the Danish islands as it spread 
into Jutland and Schleswig-Holstein. The course of this second ice-sheet is indicated by 
the direction of transport of erratics, &c, and by the trend of rock-strise and roches 
moatonnSes, as well as by the position of its terminal and lateral moraines. 

Such, then, is the glacial succession which has been established by geologists in Scandi- 
navia, North Germany, and Finland. The occurrence of two glacial epochs, separated by 
a long interval of temperate conditions, has been proved. The evidence, however, does 
not show that there may not have been more than two glacial epochs. There are certain 
phenomena, indeed, connected with the glacial accumulations of the regions in question, 
which strongly suggest that the succession of changes was more complex than is generally 
understood. Several years ago Dr A. G. Nathokst adduced evidence to show that a great 
Baltic glacier, similar to that underneath which the upper diluvium was amassed, existed 
before the advent of the vast mer de glace of the so-called " first glacial epoch,"* and his 
observations have been confirmed and extended by H. LuNDBOHM.t The facts set forth 
by them prove beyond doubt that this early Baltic glacier smoothed and glaciated the 
rocks in Southern Sweden in a direction from south-east to north-west, and accumulated 
a bottom-moraine whose included erratics yield equally cogent evidence as to the trend 
of glaciation. That old moraine is overlaid by the "lower diluvium," i.e., the boulder- 
clay of the succeeding vast mer de glace that flowed south to the foot of the Harz — the 
transport of the stones in the superjacent clay indicating a movement from N.N.E. to 
S.S.W., or nearly at right angles to the trend of the earlier Baltic glacier. It is difficult 
to avoid the conclusion that we have here to do with the products of two distinct ice- 
epochs. But hitherto no interglacial deposits have been detected between the boulder- 
clays in question. It might, therefore, be held that the earlier Baltic glacier was 
separated by no long interval of time from the succeeding great mer de glace, but may 
have been merely a stage in the development of the latter. It is at all events conceivable 
that before the great mer de glace attained its maximum extension, it might have existed 
for a time as a large Baltic glacier. I would point out, however, that if no interglacial 
beds had been recognised between the lower and the upper diluvium, geologists would 
probably have considered that the last great Baltic glacier was simply the attenuated 
successor of the preceding continental mer de glace. But we know that this was not the 
case ; the two were actually separated by a long epoch of genial temperate conditions. 

There are certain other facts that may lead us to doubt whether in the glacial 
phenomena of the Baltic coast-lands we have not the evidence of more than two glacial 
epochs. Three, and even four, boulder-clays have been observed in East and West 
Prussia. They are separated, the one from the other, by extensive aqueous deposits, 
which are sometimes fossiliferous. Moreover, the boulder-clays in question have been 

* Beskrifning. till geol. Kartbl. Trolleholm : Sveriges Geologiska Under sokning, Ser. Aa. Nr. 87. 

t Om de aldre baltiska isstrcimmen i sodra Sverige : Geolog. Forening. % Stockholm Forhandl., Bd. x. p. 157. 



GLACIAL SUCCESSION IN EUROPE. 133 

followed continuously over considerable areas. It is quite possible, of course, that all 
those boulder-clays may be the product of one epoch, laid down during more or less con- 
siderable oscillations of an ice-sheet. In this view of the case the intercalated aqueous 
deposits would indicate temporary retreats, while the boulder-clays would represent 
successive readvances of one and the same mer de glace. On the other hand, it is equally 
possible, if not more probable, that the boulder-clays and intercalated beds are evidence 
of so many separate glacial and interglacial epochs. We cannot yet say which is the 
true explanation of the facts. But these being as they are, we may doubt whether 
German glacialists are justified in so confidently maintaining that their lower and upper 
diluvial accumulations are the products of the " first " and " second " glacial epochs. 
Indeed, as I shall show presently, the upper diluvium of North Germany and Finland 
cannot represent the second glacial epoch of other parts of Europe. 

For a long time it has been supposed that the glacial deposits of the central regions of 
Eussia were accumulated during the advance and retreat of one and the same ice-sheet. 
In 1888, however, Professor Pa vlow brought forward evidence to show that the province 
of Nijni Novgorod had been twice invaded by a general mer de glace. During the first 
epoch of glaciation the ice-sheet overflowed the whole province, while only the northern 
half of the same region was covered by the mer de glace of the second invasion. Again, 
Professor Annachevsky has pointed out that in the province of Tchernigow two types of 
glacial deposits appear, so unlike in character and so differently distributed that they 
can hardly be the products of one and the same ice-sheet. But until recently no inter- 
glacial deposits had been detected, and the observations just referred to failed, therefore, 
to make much impression. The missing link in the evidence has now happily been 
supplied by M. Krischtafowitsch.* At Troizkoje, in the neighbourhood of Moscow, occur 
certain lacustrine formations which have been long known to Russian geologists. These 
have been variously assigned to Tertiary, lower glacial, postglacial, and preglacial 
horizons. They are now proved, however, to be of interglacial age, for they rest upon 
and are covered by glacial accumulations. Amongst their organic remains are oak 
(Quercus jpeduncidata), alder (Alnus glutinosa, A. incana), white birch, hazel, Norway 
maple (Acer platanoides), Scots fir, willow, water lilies (Nwphar, Nymphcea), mammoth, 
pike, perch, Anadonta, wing-cases of beetles, &c. The character of the plants shows 
that the climate of Central Eussia was milder and more humid than it is to-day. 

It is obvious that the upper and lower glacial deposits of Central Russia cannot be 
the equivalents of the upper and lower diluvium of the Baltic coast-lands. The upper 
diluvium of those regions is the bottom-moraine of the so-called great Baltic glacier. At 
the time that glacier invaded North Germany, Finland was likewise covered with ice, 
which flowed towards the south-east, but did not advance quite so far as the northern 
shores of Lake Ladoga. A double line of terminal moraines, traced from Hango Head 
on the Gulf of Finland, north-east to beyond Joensuu, puts this beyond doubt.t The 

* Bull, de la Soc. Imper. des Naturalistes de Moskau, No. 4, 1890. 

t Sederholm, Fennia, i. No. 7 ; Frosterus, ibid, iii., No. 8 ; Ramsay, ibid, iv., No. 2. 



134 PROFESSOR JAMES GEIKIE ON THE 

morainic deposits that overlie the interglacial beds of Central Kussia cannot, therefore, 
belong to the epoch of the great Baltic glacier. They are necessarily older. In short, 
it is obvious that the upper and lower glacial accumulations near Moscow must be on the 
horizon of the lower diluvium of North Germany. And if this be so, then it is clear that 
the latter cannot be entirely the product of one and the same rner de glace. When the 
several boulder-clays, described by Schroder and others as occurring in the Baltic pro- 
vinces of Germany, are reinvestigated, they may prove to be the bottom-moraines of as 
many distinct and separate glacial epochs. 

It may be contended that the glacial and interglacial deposits of Central Eussia are 
perhaps only local developments — that their evidence may be accounted for by oscillations 
of one single mer de glace. This explanation, as already pointed out, has been applied 
to the boulder-clays and intercalated aqueous beds of the lower diluvium of North 
Germany, and the prevalent character of the associated organic remains makes it appear 
plausible. It is quite inapplicable, however, to the similar accumulations in Central 
Russia. During the formation of the freshwater beds of Troizkoje, no part of Russia 
could have been occupied by an ice-sheet ; the climate was more genial and less " con- 
tinental " than the present. Yet that mild interglacial epoch was preceded and succeeded 
by extremely Arctic conditions. It is impossible that such excessive changes could have 
been confined to Central Russia. Germany, and indeed all Northern and North-Western 
Europe, must have participated in the climatic revolutions. 

So far, then, as the evidence has been considered, we may conclude that three glacial 
and two interglacial epochs at least have been established for Northern Europe. If this 
be the case, then a similar succession ought to occur in our own islands ; and a little 
consideration of the evidence already adduced will suffice to show that it does. It will 
be remembered that the lower and upper boulder-clays of the British Islands are the 
bottom-moraines of two separate and distinct ice-sheets, each of which in its time 
coalesced on the floor of the North Sea with the inland ice of Scandinavia. It is obvious, 
therefore, that our upper boulder-clay cannot be the equivalent of the upper diluvium of 
the Baltic coast-lands, of Sweden, Denmark, and Schleswig-Holstein. De Geer and 
others have shown that while the great Baltic glacier was accumulating the upper 
diluvium of North Germany, &c, the inland ice of Norway calved its icebergs at the 
mouths of the great fiords. Thus, during the so-called " second " glacial epoch of Scandi- 
navian and German geologists, the Norwegian inland ice did not coalesce with any British 
mer de glace. The true equivalent in this country of the upper diluvium is not our 
upper boulder-clay, but the great valley-moraines of our mountain regions. It is our 
epoch of large valley-glaciers which corresponds to that of the great Baltic ice-flow. Our 
upper and lower boulder-clays are on the horizon of the lower diluvium of Germany and 
the glacial deposits of Central Russia. 

It will now be seen that the evidence in Britain is fully borne out by what is known 
of the glacial succession in the corresponding latitudes of the Continent. I had inferred 
that our epoch of large valley-glaciers formed a distinct stage by itself, and was probably 



GLACIAL SUCCESSION IN EUROPE. 135 

separated from that of the preceding ice-sheet by a prolonged interval of interglacial 
conditions. One link in the chain of evidence, however, was wanting : I could not point 
to the occurrence of interglacial deposits underneath the great valley-moraines. But 
these, as we have seen, form a well-marked horizon on the Continent, and we cannot 
doubt that a similar interglacial stage obtained in these islands. We may feel confident, 
in fact, that genial climatic conditions supervened on the dissolution of the last great 
mer de glace in Britain, and that the subsequent development of extensive snow-fields 
and glaciers in our mountain regions was contemporaneous with the appearance of the 
last great Baltic glacier. 

We need not be surprised that interglacial beds should be well developed underneath 
the bottom-moraine of that great glacier, while they have not yet been recognised below 
the corresponding morainic accumulations of our Highlands and Uplands. The conditions 
in the low grounds of the Baltic coast-lands favoured their preservation, for the ice in 
those regions formed a broad mer de glace, under the peripheral areas of which sub- 
glacial erosion was necessarily at a minimum and accumulation at a maximum. In our 
mountain valleys, however, the very opposite was the case. The conditions obtaining 
there were not at all comparable to those that characterised the low grounds of Northern 
Germany, &c, but were quite analogous to those of Norway, where, as in our own 
mountain regions, interglacial beds are similarly wanting. It is quite possible, however, 
that patches of such deposits may yet be met with underneath our younger moraines, 
and they ought certainly to be looked for. But whether they occur or not in our 
mountain valleys, it is certain that some of the older alluvia of our lowlands must belong 
to this horizon. Hitherto all alluvial beds that overlie our upper boulder-clay have been 
classified as postglacial ; but since we have ascertained that our latest mer de glace was 
succeeded by genial interglacial conditions, we may be sure that records of that temperate 
epoch will yet be recognised in such lowland tracts as were never reached by the glaciers 
of the succeeding cold epoch. Hence, I believe that some of our so-called " postglacial " 
alluvia will eventually be assigned to an interglacial horizon. Amongst these may be 
cited the old peat and freshwater beds that rest upon the upper boulder-clay at Hailes 
Quarry, near Edinburgh. To the same horizon, in all probability, belong the clays, with 
Megaceros, &c, which occur so frequently underneath the peat-bogs of Ireland. An 
interesting account of these was given some years ago by Mr Williams,* who, as a 
collector of Megaceros remains, had the best opportunity of ascertaining the nature of 
the deposits in which these occur. He gives a section of Ballybetagh Bog, nine miles 
south-east of Dublin, which is as follows : — 

6. Peat. 

5. Greyish clay. 

4. Brownish clay, with remains of Megaceros. 

3. Yellowish clay, largely composed of vegetable matter. 

2. Fine tenacious clay, without stones. 

1. Boulder-clay. 

* Geol. Mag., 1881, p. 354. 
VOL. XXXVII. PART I. (NO. 9). Y 



136 PROFESSOR JAMES GEIKIE ON THE 

The beds overlying the boulder-clay are evidently of lacustrine origin. The fine clay 
(No. 2), according to Mr Williams, is simply reconstructed boulder- clay. After the 
disappearance of the mer de glace the land would for some time be practically destitute 
of any vegetable covering, and rain would thus be enabled to wash down the finer 
ingredients of the boulder-clay that covered the adjacent slopes, and sweep them into the 
lake. The clay formed in this way is described as attaining a considerable thickness near 
the centre of the old lake, but thins off towards the sides. The succeeding bed (No. 3) 
consists so largely of vegetable debris that it can hardly be called a clay. Mr Williams 
describes it as a " bed of pure vegetable remains that has been ages under pressure." He 
notes that there is a total absence in this bed of any tenacious clay like that of the under- 
lying stratum, and infers, therefore, that the rainfall during the growth of the lacustrine 
vegetation was not so great as when the subjacent clay was being accumulated. Eemains 
of Megaceros occur resting on the surface of the plant-bed and at various levels in the 
overlying brownish clay, which attains a thickness of 3 to 4 feet. The latter is a true 
lacustrine sediment, containing a considerable proportion of vegetable matter, inter- 
stratified with seams of clay and fine quartz-sand. According to Mr Williams, it was 
accumulated under genial or temperate climatic conditions like the present. Between 
this bed and the overlying greyish clay (30 inches to 3 feet thick) there is always in all 
the bog deposits examined by Mr Williams a strongly-marked line of separation. The 
greyish clay consists exclusively of mineral matter, and has evidently been derived from 
the disintegration of the adjacent granitic hills. Mr Williams is of opinion that this 
clay is of aqueo-glacial formation. This he infers from its nature and texture, and from 
its abundance. " Why," he asks, " did not this mineral matter come down in like 
quantity all the time of the deposit of the brown clay which underlies it ? Simply 
because, during the genial conditions which then existed, the hills were everywhere 
covered with vegetation ; when the rain fell it soaked into the soil, and the clay being 
bound together by the roots of the grasses, was not washed down, just as at the present 
time, when there is hardly any degradation of these hills taking place." He mentions, 
further, that in the grey clay he obtained the antler of a reindeer, and that in one case 
the antlers of a Megaceros, found embedded in the upper surface of the brown clay, 
immediately under the grey clay, were scored like a striated boulder, while the under 
side showed no markings. Mr Williams also emphasizes the fact that the antlers of 
Megaceros frequently occur in a broken state — those near the surface of the brown clay 
being most broken, while those at greater depths are much less so. He shows that this 
could not be the result of tumultuous river-action — the elevation of the valley precluding 
the possibility of its receiving a river capable of producing such effects. Moreover, the 
remains show no trace of having been water-worn, the edges of the teeth of the great 
deer being as sharp as if the animal had died but yesterday. Mr Williams thinks that 
the broken state of the antlers is due to the " pressure of great masses of ice on the 
surface of the clay in which they were embedded, the wide expanse of the palms of the 
aDtlers exposing them to pressure and liability to breakage ; and even, in many instances, 



GLACIAL SUCCESSION IN EUROPE. 137 

when there was 12 or 14 inches in circumference of solid bone almost as hard and sound 
as ivory, it was snapped across." It is remarkable that in this one small bog nearly one 
hundred heads of Megaceros have been dug up. 

Mr Williams' observations show us that the Megaceros-beds are certainly older than 
the peat-bogs with their buried timber. When he first informed me of the result of his 
researches (1880), I did not believe the Megaceros-beds could be older than the latest 
cold phase of the Ice Age. I thought that they were later in date than our last general 
mer de glace, and I think so still, for they obviously rest upon its ground-moraine. But 
since I now recognise that our upper boulder-clay is not the product of the last glacial 
epoch, it seems to me highly probable that the Megaceros-beds are of interglacial age — » 
that, in short, they occupy the horizon of the interglacial deposits of North Germany, &c.; 
The appearances described by Mr Williams in connection with the "grey clay" seem 
strongly suggestive of ice-action. Ballybetagh Bog occurs at an elevation of 800 feet 
above the sea, in the neighbourhood of the Three Rock Mountains (1479 feet), and during 
the epoch of great valley-glaciers the climatic conditions of that region must have been 
severe. But, without having visited the locality in question, I should hesitate to say 
that the phenomena necessarily point to local glaciation. Probably frost, lake-ice, and 
thick accumulations of snow and neve might suffice to account for the various facts cited 
by Mr Williams. 

I have called special attention to these Irish lacustrine beds, because it is highly 
probable that the postglacial age of similar alluvia occurring in many other places in 
these islands has hitherto been assumed and not proved. Now that we know, however,; 
that a long interglacial stage succeeded the disappearance of the last general mer de 
glace, we may feel sure that the older alluvia of our lowland districts cannot belong 
exclusively to postglacial times. The local ice-sheets and great glaciers of our "third" 
glacial epoch were confined to our mountain regions ; and in the Lowlands, therefore, 
which were not invaded, we ought to have the lacustrine and fluviatile accumulations b£ 
the preceding interglacial stage. A fresh interest noW. attaches to our older alluvia, 
which must be carefully re-examined in the new light thus thrown upon them. 

Turning next to the Alpine Lands of Central Europe, we find that geologists there 
have for many years recognised two glacial epochs. Hence, like their confreres in 
Northern Europe, they speak of "first" and "second" glacial epochs.* Within recent 
years, however, Professor Penck has shown that the Alps have experienced at least three 
separate periods of glaciation. He describes three distinct ground-moraines, with 
associated river-terraces and interglacial deposits in the valleys of the Bavarian Alps, 
and his observations have been confirmed by Professor Bruckner and Dr Bohm. t The 

* Morlot, Bulletin de la Soc. Vaud. d. Sciences nat., 1854, 1858, 1860 ; Deicke, Bericht. d. St. Gall, naturf. ges., 
1858 ; Heer, Urwelt der Schweiz; Mohlberg, Festschrift d. aarg. naturf. Ges. z. Feier ihrer 500 Site., 1869 ; Rothpletz, 
Denkschr. d. schweizer. Ges. f. d. ges. Naturwissensch., Bd. xxviii., 1881 ; Wettstein, Geologie v. Zurich u. Umgebung, 
1885 ; Baltzer, Mitteil. d. naturf. Ges Bern, 1887 ; Renevier, Bull, de la Soc. helvet. d. Sciences nat., 1887. 

t Penck, Die Vergletscherung d. deutschen .Alpen, 1882 ; Bruckner, " Die Vergletscherung des Salzachgebietes," 
Geogr. Abliandl. Witn, Bd. i. ; Bohm, Jahrb. der Jc. h. geol. Beichsanst, 1884, 1885 ; see also O. Fraas, Neues Jahrb. f. 
Min. Geol. u. Palceont., 1880, Bd. i. p. 218; E. Fugger and C. Kastner, Verhandl. d. k. Jc. geol. Beichsanst, 1883, p. 136. 



138 PROFESSOR JAMES GEIKIE ON THE 

same glacialists, I understand, have nearly completed an elaborate survey of the Eastern 
Alps, of which they intend shortly to publish an extended account. The results obtained 
by them are very interesting, and fully bear out the conclusions already arrived at from 
their exploration of the Bavarian Alps.* A similar succession of glacial epochs has quite 
recently been determined by Dr Du Pasquier in North Switzerland, t Nor is this kind 
of evidence confined to the north side of the Alps. On the shores of Lake Garda, 
between Salb and Brescia, three ground-moraines, separated by interglacial accumulations, 
are seen in section. The interglacial deposits consist chiefly of loams — the result of 
subaerial weathering — and attain a considerable thickness. From this Penck infers that 
the time which has elapsed since the latest glaciation is less than that required for the 
accumulation of either of the two interglacial series — a conclusion which, he says, is 
borne out by similar observations in other parts of the Alpine region. J 

Although the occurrence of such subaerial products intercalated between separate 
morainic accumulations is evidence of climatic changes, still it does not tell us how far 
the glaciers retreated during an interglacial stage. Fortunately, however, lignite beds 
and other deposits charged with plant remains are met with occupying a similar position, 
and from these we gather that during interglacial times the glaciers sometimes retired to 
the very heads of the mountain valleys, and must have been smaller than their present 
representatives. Of such interglacial plant-beds, which have been met with in some 
twenty localities, the most interesting, perhaps, is the breccia of Hotting, in the neigh- 
bourhood of Innsbruck. § This breccia rests upon old morainic accumulations, and is 
again overlaid by the later moraines of the great Inn glacier. From the fact that the 
breccia contains a number of extinct species of plants, palaeontologists were inclined to 
assign it to the Pliocene. Professor Penck, however, prefers to include it in the 
Pleistocene system, along with all the glacial and interglacial deposits of the Alpine 
lands. According to Dr von Wettstein, the flora in question is not Alpine but Pontic. 
At the time of the formation of the breccia the large-leaved Rhododendron ponticum 
flourished in the Inn valley at a height of 1200 metres above the sea; the whole 
character of the flora, in short, indicates a warmer climate than is now experienced in 
the neighbourhood of Innsbruck. It is obvious, therefore, that in interglacial times 
the glaciers must have shrunk back, as Professor Penck remarks, to the highest ridges 
of the mountains. 

We may now glance at the glacial succession which has been established for Central 
France. More than twenty years ago Dr Julien brought forward evidence to show 
that the region of the Puy de Dome had witnessed two glacial epochs. |l During the 

* Mittheil. des deutsch. u. oesterreich. Alpenvereins, 1890, No. 20 u. 23. 

+ Beitrdge z. geolg. Karte der Schweiz, 31 Lief., 1891 ; Archiv. d. Sciences phys. et nat., 1891, p. 44. 

| " Die grosse Eiszeit," Hirnmel u. Erde. 

§ Penck, Die Vergletscherung der deutschen Alpen, p. 228 ; Verhandl. d. k. k. geol. Reichsanst., 1887, No. 5 ; Himmel 
und Erde, 1891. Bohm, Jahrb. d. k. k. geol. Reichsanst., 1884, p. 147. Blaas, Ferdinandeums Zeitschr., iv. Folge ; 
Bericht. d. nat.-wissensch. Vereins, 1889, p. 97. 

|| Des ph.4norn.hxes glaciaires dans le Plateau central de la France, &c, Paris, 1869. 



GLACIAL SUCCESSION IN EUKOPE. 139 

first of these epochs a large glacier flowed from Mont Dore. After its retreat a prolonged 
interglacial epoch followed, during which the old morainic deposits and the rocks they 
rest upon were much eroded. In the valleys and hollows thus excavated freshwater 
beds occur which have yielded relics of an abundant flora, together with the remains of 
Elephas rneridionalis, Rhinoceros leptorhinus, &c. After the deposition of these fresh- 
water alluvia, glaciers again descended the valleys and covered the interglacial beds with 
their moraines. Similar results have been obtained by M. Rames from a study of the 
glacial phenomenon of Cantal, which he shows belong to two separate epochs. 4 ' 5 ' The 
interval between the formation of the two series of glacial accumulations must have been 
prolonged, for the valleys during that interval were in some places eroded to a depth of 
900 feet. M. Rames further recognises that the second glacial epoch was distinguished 
by two advances of valley-glaciers, separated by a marked episode of fusion. Dr Julien 
has likewise noted the evidence for two episodes of fusion during the first extension of 
the glaciers of the Puy de Dome. 

Two glacial epochs have similarly been admitted for the Pyrenees ; t but Dr Penck 
some years ago brought forward evidence to show that these mountains, like the Alps, 
have experienced three separate and distinct periods of glaciation. J 

We may now return to Scotland, and consider briefly the changes that followed upon 
the disappearance of the local ice-sheets and large valley -glaciers of our mountain regions. 
The evidence is fortunately clear and complete. In the valley of the Tay, for example, 
at and below Perth, we encounter the following succession of deposits : — 

6. Recent alluvia. 

5. Carse-deposits, 45 feet above sea-level. 

4. Peat and forest bed. 

3. Old alluvia. 

2. Clays, &c, of 100-feet beach. 

1. Boulder-clay. 

The old alluvia (3) are obviously of fluviatile origin, and show us that after the 
deposition of the clays, &c, of the 100-feet beach the sea retreated, and allowed the Tay 
and its tributaries to plough their way down through the marine and estuarine deposits 
of the " third " glacial epoch. These deposits would appear to have extended at first as 
a broad and approximately level plain over all the lower reaches of the valleys. Through 
this plain the Tay and the Earn cut their way to a depth of more than 100 feet, and 
gradually removed all the material over a course which can hardly be less than 2 miles 
in breadth below the Bridge of Earn, and considerably exceeds that in the Carse of 
Gowrie. No organic remains occur in the " old alluvia," but the deposits consist princi- 
pally of gravel and sand, and show not a trace of ice-action. Immediately overlying 

* Bull. Soc. gM. de France, 1884 ; see also M. Boule, Bull, de la Soc. philomath, de Paris, 8 e Ser. i. p. 87. 
t Garrigou, Bull. Soc. gM. de France, 2 e Ser. xxiv. p. 577 ; Jeanbernat, Bull, de la Soc. d'Hist. nat. de Toulouse, 
iv. pp. 114, 138 ; Piette, Bull. Soc. gM. de France, 3 e Ser. ii. pp. 503, 507. 
J Mitteilungen d. Vereinsf. Erdhunde zu Leipzig, 1883. 



140 PROFESSOR JAMES GEIKIE ON THE 

them comes the well-known peat-bed (4). This is a mass of vegetable matter, varying 
in thickness from a few inches up to 3 or 4 feet. In some places it seems to be made 
up chiefly of reed-like plants and sedges and occasional mosses, commingled with which 
are abundant fragments of birch, alder, willow, hazel, and pine. In other places it 
contains trunks and stools of oak and hazel, with hazel-nuts — the trees being rooted in 
the subjacent deposits. It is generally highly compressed and readily splits into laminae, 
upon the surface of which many small reeds, and now and again wing-cases of beetles, 
may be detected. A large proportion of the woody debris — twigs, branches, and trunks 
— appears to have been drifted. A " dug-out " canoe of pine was found, along with 
trunks of the same tree, in the peat at Perth. The Carse-deposits (5), consisting 
principally of clay and silt, rest upon the peat-bed. The occurrence in these deposits of 
Scrobicularia piperata and oyster-shells leaves us in no doubt as to their marine origin. 
They vary in thickness from 10 up to fully 40 feet.* 

A similar succession of deposits is met with in the valley of the Forth, t and we can- 
not doubt that these tell precisely the same tale. I have elsewhere | adduced evidence 
to show that the peat-bed, with drifted vegetable debris, which underlies the Carse 
accumulations of the Forth and Tay is on the same horizon as the " lower buried forest " 
of our oldest peat-bogs, and the similar bogs that occur in Norway, Sweden, Denmark, 
Schleswig-Holstein, Holland, &c. Underneath the " lower buried forest " of those regions 
occur now and again freshwater clays, charged with the relics of an Arctic-alpine flora ; 
and quite recently similar plant-remains have been detected in old alluvia at Corstorphine, 
near Edinburgh. When the beds below our older peat-bogs are more carefully examined, 
traces of that old Arctic flora will doubtless be met with in many other parts of these 
islands. It was this flora that clothed North- Western Europe during the decay of the 
last local ice-sheets of Britain and the disappearance of the great Baltic glacier. 

The dissolution of the large valley- glaciers of this country was accompanied by a 
general retreat of the sea — all the evidence leading to the conviction that our islands 
eventually became united to the Continent. The climatic conditions, as evidenced by 
the flora of the " lower buried forest," were decidedly temperate — probably even more 
genial than they are now, for the forests attained at that time a much greater horizontal 
and vertical range. This epoch of mild climate and continental connection was even- 
tually succeeded by one of submergence, accompanied by colder conditions. Britain was 
again insulated — the sea-level in Scotland reaching a height of 45-50 feet above present 
high-water. To this epoch pertain the Carse-clays of the Forth and Tay. A few erratics 
occur in these deposits, probably betokening the action of floating ice, but the beds more 
closely resemble the modern alluvial silts of our estuaries than the tenacious clays of the 
100-feet terrace. When the Carse-clays are followed inland, however, they pass into 
coarse river-gravel and shingle, forming a well-marked high-level alluvial terrace, of much 

* For a particular account of the Tay-valley Succession, see Prehistoric Europe, p. 385. 

+ Proc. Roy. Soc. Edin., 1883-84, p. 745 ; Mem. Geol. Survey, Scotland, Explanation of Sheet 31. 

\ Prehistoric Europe, chaps, xvi., xvii. 



GLACIAL SUCCESSION IN EUROPE". 141 

the same character as the yet higher-level fluviatile terrace, which is associated in like 
manner with the marine deposits of the 100-feet beach. 

Of contemporaneous age with the Carse-clays, with which indeed they are continuous, 
are the raised beaches at 45-50 feet. These beaches occur at many places along the 
Scottish coasts, but they are seldom seen at the heads of our sea-lochs. When the sea 
stood at this level, glaciers of considerable size occupied many of our mountain valleys. 
In the west they came down in places to the sea-coast, and dropped their terminal 
moraines upon the beach-deposits accumulating there. Thus, in Arran * and in Suther- 
land^ these moraines are seen reposing on the raised beaches of that epoch. And I 
think it is probable that the absence of such beaches at the heads of many of the sea- 
lochs of the Highland area is to be explained by the presence there of large glaciers, 
which prevented their formation. 

Thus, there is clear evidence to show that after the genial epoch represented by the 
"lower buried forest," a recrudescence of glacial conditions supervened in Scotland. 
Many of the small moraines that occur at the heads of our mountain valleys, both in the 
Highlands and Southern Uplands, belong in all probability to this epoch. They are 
characterised by their very fresh and well-preserved appearance. J It is not at all likely 
that these later climatic changes could have been confined to Scotland. Other regions 
must have been similarly affected. But the evidence will probably be harder to read 
than it is with us. Had it not been for the existence of our "lower buried forest," with 
the overlying Carse-deposits, we could hardly have been able to distinguish so readily 
between the moraines of our " third " glacial epoch and those of the later epoch to which 
I now refer. The latter, we might have supposed, simply marked a stage in the final 
retreat of the antecedent great valley-glaciers. 

I have elsewhere traced the history of the succeeding stages of the Pleistocene period, and 
adduced evidence of similar, but less strongly-marked, climatic changes having followed 
upon those just referred to, and my conclusions have been supported by the independent 
researches of Professor Blytt in Norway. But these later changes need not be considered 
here. It is sufficient for my general purpose to confine attention to the well-proved 
conclusion that after the decay of the last local ice-sheets and great glaciers of our " third" 
glacial epoch genial conditions obtained, and that these were followed by cold and humid 
conditions, during the prevalence of which glaciers re-appeared in many mountain valleys. 

We have thus, as it seems to me, clear evidence in Europe of four glacial epochs, 
separated the one from the other by protracted intervals of genial temperate conditions. 
So far, one's conclusions are based on data which cannot be gainsaid, but there are certain 
considerations which lead to the suspicion that the whole of the complex tale has not yet 
been unravelled, and that the climatic changes were even more numerous than those that 
I have indicated. Let it be noted that glacial conditions attained their maximum during 

* British Association Reports (1854) : Trans, of Sections, p. 78. 

t L. Hinxman: Paper read before Edin. Geol. Soc, April 1892. 

| Prehistoric Europe (chaps, xvi. xvii.) gives a fuller statement of the evidence. 



142 PROFESSOR JAMES GETKIE ON THE 

the earliest of our recognised glacial epochs. With each recurring cold period the ice- 
sheets and glaciers successively diminished in importance. That is one of the outstanding 
facts with which we have to deal. Whatever may have been the cause or causes of 
glacial and interglacial conditions, it is obvious that those causes, after attaining a 
maximum influence, gradually became less effective in their operation. Such having been 
the case, one can hardly help suspecting that our epoch of greatest glaciation may have 
been preceded by an alternation of cold and genial stages analogous to those that followed 
it. If three cold epochs of progressively diminished severity succeeded the epoch of 
maximum glaciation, the latter may have been preceded by one or more epochs of 
progressively increased severity. That something of the kind may have taken place is 
suggested by the occurrence of the old moraine of that great Baltic glacier that preceded 
the appearance of the most extensive mer de glace of Northern Europe. The old moraine 
in question, it will be remembered, underlies the " lower diluvium." Unfortunately, the 
very conditions that attended the glaciation of Europe render it improbable that any 
conspicuous traces of glacial epochs that may have occurred prior to the period of 
maximum glaciation could have been preserved within the regions covered by the great 
inland ice. Their absence, therefore, cannot be held as proving that the lower boulder- 
clays of Britain and Northern Europe are the representatives of the earliest glacial epoch. 
The lowest boulder- clay, I believe, has yet to be discovered. 

It is in the Alpine lands that we encounter the most striking evidence of glacial 
conditions anterior to the epoch of maximum glaciation. The famous breccia of 
Hotting has already been referred to as of interglacial age. From the character of its 
flora, Ettinghausen considered this accumulation to be of Tertiary age. The assemblage 
of plants is certainly not comparable to the well-known interglacial flora of Durnten. 
According to the researches of Dr R. von Wettstein,* the Hotting flora has most affinity 
with that of the Pontic Mountains, the Caucasus, and Southern Spain, and implies a 
considerably warmer climate than is now experienced in the Inn valley. This remarkable 
deposit, as Dr Penck pointed out some ten years ago, is clearly of interglacial age. His 
conclusions were at once challenged, on the ground that the flora had a Tertiary and not 
a Pleistocene facies ; consequently, it was urged that, as all glacial deposits were of 
Pleistocene age, this particular breccia could not be interglacial. But in this, as in 
similar cases, the palaeontologist's contention has not been sustained by the strati- 
graphical evidence, and Dr Penck's observations have been confirmed by several highly- 
competent geologists, as by MM. Bohm and Du Pasquier. The breccia is seen in several 
well-exposed sections resting upon the moraine of a local glacier which formerly descended 
the northern flanks of the Inn Valley, opposite Innsbruck, where the mountain-slopes 
under existing conditions are free from snow and ice. Nor is this all, for certain erratics 
appear in the breccia, which could only have been derived from pre-existing glacial 
accumulations, and their occurrence in this accumulation at a height of 1150 metres 
shows that before the advent of the Hotting flora the whole Inn Valley must have been 

* Sitzungsberichte d. Kais. Acad. d. Wissensch. in Wim } mathem.-naturw. Classe, Bd. xcvii. Abth. i., 1888. 



GLACIAL SUCCESSION IN EUROPE. 143 

filled with ice. The plant-bearing beds are in their turn covered by the ground-moraine 
of a later and more extensive glaciation. To bring about the glacial conditions that 
obtained before the formation of the breccia, the snow-line, according to Pence, must 
have been at least 1000 metres lower than now ; while, to induce the succeeding 
glaciation, the depression of the snow-line couJd not have been less than 1200 metres. 
These observations have been extended to many other parts of the Alps, and the con- 
clusion arrived at by Professor Penck and his colleagues, Professor Bruckner, and Dr 
Bohm, is briefly this, — that the maximum glaciation of those regions did not fall in the 
" first " but in the " second " Alpine glacial epoch. 

The glacial phenomena of Northern and Central Europe are so similar — the climatic 
oscillations which appear to have taken place had so much in common, and were on so 
grand a scale — that we cannot doubt they were synchronous. We may feel sure, 
therefore, that the epoch of maximum glaciation in the Alps was contemporaneous with 
the similar epoch in the north. And if this be so, then in the oldest ground-moraines of 
the Alps we have the records of an earlier glacial epoch than that which is represented 
by the lower boulder-clays of Britain and the corresponding latitudes of the Continent. 
In other words, the Hotting flora belongs to an older stage of the Glacial Period than 
any of the acknowledged interglacial accumulations of Northern Europe. The character 
of the plants is in keeping with this conclusion. The flora has evidently much less 
connection with the present flora of the Alps than the interglacial floras of Britain and 
Northern Europe have with those that now occupy their place. The Hotting flora, 
moreover, implies a considerably warmer climate than now obtains in the Alpine regions, 
while that of our interglacial beds indicates a temperate insular climate, apparently much 
like the present. 

The high probability that oscillations of climate preceded the advent of the so-called 
" first" mer de glace of Northern Europe must lead to a re-examination of our Pliocene 
deposits, with a view to see whether these yield conclusive evidence against such climatic 
changes having obtained immediately before Pleistocene times. By drawing the line of 
separation between the Pleistocene and the Pliocene at the base of our glacial series, the 
two systems in Britain are strongly marked off the one from the other. There is, in 
short, a distinct " break in the succession." From the Cromer Forest-bed, with its 
abundant mammalian fauna and temperate flora, we pass at once to the overlying Arctic 
freshwater bed and the superjacent boulder-clay that marks the epoch of maximum 
glaciation.* Amongst the mammalian fauna of the Forest-bed are elephants {Elephas 
meridionalis, E. antiquus), hippopotamus, rhinoceros (R. etruscus), horses, bison, boar, 
and many kinds of deer, together with such carnivores as bears, Machwrodus, spotted 
hyaena, &c. The freshwater and estuarine beds which contain this fauna rest immediately 
upon marine deposits (Weybourn Crag), the organic remains of which have a decidedly 
Arctic facies. Here, then, we have what at first sight would seem to be another break 

* In some places, however, certain marine deposits (Leda-myalis bed) immediately overlie the Forest-bed. See 
postea, footnote, p. 145. 

VOL. XXXVII. PART I. (NO. 9). Z 



144 PROFESSOR JAMES GEIKIE ON THE 

iii the succession. The Forest-bed, one might suppose, indicated an interglacial epoch, 
separating two cold epochs. But Mr Clement Eeid, who has worked out the geology of 
the Pliocene with admirable skill,* has another explanation of the phenomena. It has 
lonsf been known that the organic remains of the marine Pliocene of Britain denote a 
progressive lowering of temperature. The lower member of the system is crowded with 
southern forms, which indicate warm-temperate conditions. But when we leave the 
Older and pass upwards into the Newer Pliocene those southern forms progressively 
disappear, while at the same time immigrants from the north increase in numbers, until 
eventually, in the beds immediately underlying the Forest-bed, the fauna presents a 
thoroughly Arctic facies. During the formation of the Older Pliocene with its southern 
fauna our area was considerably submerged, so that the German Ocean had then a much 
wider communication with the seas of lower latitudes. At the beginning of Newer 
Pliocene times, however, the land emerged to some extent, and all connection between 
the German Ocean and more southern seas was cut off. When at last the " Forest-bed 
series " began to be accumulated, the southern half of the North Sea basin had become 
dry land, and was traversed by the Ehine in its course towards the north, the Forest- 
bed representing the alluvial and estuarine deposits of that river. 

Mr Eeid, in referring to the progressive change indicated by the Pliocene marine 
fauna, is inclined to agree with Professor Peestwich that this was not altogether the 
result of a general climatic change. He thinks the successive dying out of southern 
forms and the continuous arrival of boreal species was principally due to the North Sea 
remaining fully open to the north, while all connection with southern seas was cut off. 
Under such conditions, he says, " there was a constant supply of Arctic species brought 
by every tide or storm, while at the same time the southern forms had to hold their own 
without any aid from without ; and if one was exterminated it could not be replaced." 
Doubtless the isolation of the North Sea must have hastened the extermination of the 
southern forms, but the change could not have been wholly due to such local causes. 
Similar, if less strongly-marked, changes characterise the marine Pliocene of the Medi- 
terranean area, while the freshwater alluvia of France, &c, furnish evidence in the same 
direction. 

The Cromer Forest-bed overlies the Weybourn Crag, the marine fauna of which 
has a distinctly Arctic facies. The two cannot, therefore, be exactly contemporaneous : 
the marine equivalents of the Forest-bed are not represented. But Mr Eeid points out 
that several Arctic marine shells of the Weybourn Crag occur also in the Forest-bed, 
while certain southern freshwater and terrestrial shells common in the latter are met with 
likewise in the former, commingled with the prevailing Arctic marine species. He thinks, 
therefore, that we may fairly conclude that the two faunas occupied adjacent areas. 
One can hardly accept this conclusion without reserve. It is difficult to believe that a 
temperate flora and mammalian fauna like that of the Forest-bed clothed and peopled 
Eastern England when the adjacent sea was occupied by Arctic molluscs, &c. Surely 

* Mem. of Geol. Survey, " Pliocene Deposits of Britain." 



GLACIAL SUCCESSION IN EUROPE. 145 

the occurrence of a few forms, which are common to the Forest -bed and the underlying 
Crag, does not necessarily prove that the two faunas occupied adjacent districts. Mr 
Eeid, indeed, admits that some of the marine shells in the Forest-bed series may have 
been derived from the underlying Crag. Were the marine equivalents of the Forest>bed 
forthcoming we might well expect them to contain many Crag forms, but the facies of 
the fauna would most probably resemble that of the existing North Sea fauna. Again, 
the appearance in the Weybourn Crag of a few southern shells common to the Forest- 
bed, does not seem to prove more than that such shells were contemporaneous somewhere 
with an Arctic marine fauna. But it is quite possible that they might have been carried 
for a long distance from the south ; and, even if they actually existed in the near 
neighbourhood of an Arctic marine fauna, we may easily attach too much importance to 
their evidence.* I cannot think, therefore, that Mr Eeid's conclusion is entirely satis- 
factory. After all, the Cromer Forest-bed rests upon the Weybourn Crag, and the 
evidence as it stands is explicable in another way. It is quite possible, for example, that 
the Forest-bed really indicates an epoch of genial or temperate conditions, preceded, as it 
certainly was eventually succeeded, by colder conditions. 

If it be objected that this would include as interglacial what has hitherto been regarded 
by most as a Pliocene mammalian fauna,t I would reply that the interglacial age of 
that fauna has already been proved in Central France. The interglacial beds of Auvergne, 
with JSlephas meridionalis, rest upon and are covered by moraines, J and with these have 
been correlated the deposits of Saint-Prest. Again, in Northern Italy the lignites of Leffe 
and Pianico, which, as I showed a number of years ago, § occupy an interglacial position, 
have likewise yielded Elephas meridionalis and other associated mammalian forms. 

* The inference that the Forest-bed occupies an interglacial position is strengthened by the evidence of certain 
marine deposits which immediately overlie it. These (known collectively as the Leda-myalis bed) occur in irregular 
patches, which, from the character of their organic remains, cannot all be precisely of the same age. In one place, for 
example, they are abundantly charged with oysters, having valves united, and with these are associated other species of 
molluscs that still live in British Seas. At another place no oysters occur, but the beds yield two Arctic shells, Leda 
myalis and Astarte borealis, and some other forms which have no special significance. Professor Otto Torell pointed 
out to Mr Reid that these separate deposits could not be of the same age, for the oyster is sensitive to cold and does 
not inhabit the seas where Leda myalis and Astarte borealis flourish. From a consideration of this and other evidence 
Mr Reid concludes that it is possible that the deposits indicate a period of considerable length, during which the depth 
of water varied and the climate changed. Two additional facts may be noted : Leda myalis does not occur in any of 
the underlying Pliocene beds, while the oyster is not found in the Weybourn and Chillesford Crag, though common 
lower down in the Pliocene series. These facts seem to me to have a strong bearing on the climatic conditions of the 
Forest-bed epoch. They show us that the oyster flourished in the North Sea before the period of the Weybourn Crag 
— that it did not live side by side with the Arctic forms of that period — and that it reappeared in our seas when favour- 
able conditions returned. When the climate again became cold an Arctic fauna (including a new-comer, Leda myalis) 
once more occupied the North Sea. 

+ Elephas meridionalis is usually regarded as a type-form of the Newer Pliocene, but long ago Dr Fdchs pointed 
out that in Hungary this species is of quaternary age : Verhandl. d. k. k. geolog. Beiehsanstalt, 1879, pp. 49, 270. 
It matters little whether we relegate to the top of the Pliocene or to the base of the Pleistocene the beds in 
which this species occurs. That it is met with upon an interglacial horizon is certain ; and if we are to make the 
Pleistocene co-extensive with the glacial and interglacial series, we shall be compelled to include in that system some 
portion of the Newer Pliocene. 

% Julien, Des Phe'nomenes glaciaires dans le Plateau central, &c, 1869 ; Boule, Revue d'Anthropologie, 1879. 

§ Prehistoric Europe, p. 306. Professor Pence writes me that he and the Swiss glacialist, Dr Du Pasquier, have 
recently examined these deposits, and are able to confirm my conclusion as to their interglacial position. 



146 



PROFESSOR JAMES GEIKIE ON THE 



There can be no doubt, then — indeed it is generally admitted — that the cold 
conditions that culminated in our Glacial Period began to manifest themselves in Pliocene 
times. Moreover, as it can be shown that Elephas meridionalis and its congeners 
lived in Central Europe after an epoch of extensive glaciation, it is highly probable that 
the Forest-bed, which contains the relics of the same mammalian fauna, is equivalent in 
age to the early interglacial beds of France and the Alpine Lands. We seem, therefore, 
justified in concluding that the alternation of genial and cold climates that succeeded the 
disappearance of the greatest of our ice-sheets was preceded by analogous climatic changes 
in late Pliocene times. 

I shall now briefly summarise what seems to have been the glacial succession in 
Europe : — 



Glacial 



1. Weybourn Crag ; ground-moraine of great Baltic Glacier underlying " lower 
diluvium ; " oldest recognised ground-moraines of Central Europe. 

These accumulations represent the earliest glacial epoch of which any trace has 
been discovered. It would appear to have been one of considerable severity, but not 
so severe as the cold period that followed. 



f 2. Forest-bed of Cromer; Hotting breccia; lignites of Leffe and Pianico; inter- 
iDterglacial . \ glacial beds of Central France. 

[ Earliest recognised interglacial epoch ; climate very genial. 



Glacial 



3. Lower boulder-clays of Britain; lower diluvium of Scandinavia and North 
Germany (in part); lower glacial deposits of South Germany and Central Russia; 
ground-moraines and high-level gravel-terraces of Alpine Lands, &c. ; terminal 
moraines of outer zone. 

The epoch of maximum glaciation ; the British and Scandinavian ice-sheets con- 
(. fluent ; the Alpine glaciers attain their greatest development. 



Interglacial 



4. Interglacial freshwater alluvia, peat, lignite, &c, with mammalian remains 
(Britain, Germany, &c, Central Russia, Alpine Lands, &c.) ; marine deposits (Britain, 
Baltic coast-lands). 

Continental condition of British area ; climate at first cold, but eventually tem- 
perate. Submergence ensued towards close of the period, with conditions passing from 
. temperate to Arctic. 



Glacial 



5. Upper boulder-clay of Britain ; lower diluvium of Scandinavia, Germany, &c, 
in part ; upper glacial series in Central Russia ; ground- moraines and gravel-terraces 
in Alpine Lands. 

Scandinavian and British ice-sheets again confluent, but oner de glace does not 
extend quite so far as that of the preceding cold epoch. Conditions, however, much 
more severe than those of the next succeeding cold epoch. Alpine glaciers deposit 
b the moraines of the inner zone. 



GLACIAL SUCCESSION IN EUROPE. 



147 



6. Freshwater alluvia, lignite, peat, &c. (some of the so-called postglacial alluvia of 
Britain ; interglacial beds of North Germany, &c. ; Alpine lands (?) ; marine deposits 
Interglacial . j °f Britain and Baltic coast-lands). 

Britain probably again continental ; climate at first temperate and somewhat 
insular; submergence ensues with cold climatic conditions — Scotland depressed for 
100 feet ; Baltic provinces of Germany, &c, invaded by the waters of the North Sea. 



Glacial 



7. Ground-moraines, terminal moraines, &c, of mountain regions of Britain ; upper 
diluvium of Scandinavia, Finland, North Germany, &c; great terminal moraines of same 
regions ; terminal moraines in the large longitudinal valleys of the Alps (Penck). 

Major portion of Scottish Highlands covered by ice-sheet ; local ice-sheets in 
Southern Uplands of Scotland and mountain districts in other parts of Britain; great 
valley-glaciers sometimes coalesce on low grounds ; icebergs calved at mouths of 
Highland sea-lochs ; terminal moraines dropped upon marine deposits then forming 
(100-feet beach). Scandinavia shrouded in a great ice-sheet, which broke away in ice- 
bergs along the whole west coast of Norway. Epoch of the last great Baltic glacier. 



Interglacial . 



f 8. Freshwater alluvia (with Arctic plants) ; " lower buried forest and peat " (Britain 
and North-west Europe generally). Carse-clays and raised beaches of 45-50-feet 
level in Scotland. 

Britain again continental; climate at first cold, subsequently becoming temperate: 
great forests. Eventual insulation of Britain ; climate humid, and probably colder 
than now. 



Glacial 



f 9. Local moraines in mountain-valleys of Britain, here and there resting on 45-50- 
feet beach ; so-called " postglacial " moraines in the upper valleys of the Alps. 

Probably final appearance of glaciers in our islands. Some of these glaciers attained 
a considerable size, reaching the sea and shedding icebergs. It may be noted here 
that the decay of these latest glaciers was again followed by emergence of the land 

k and a recrudescence of forest-growth (" upper buried forest "). 



A word of reference may now be made to that remarkable association of evidence of 
submergence, with proofs of glacial conditions, which has so frequently been noted by 
geologists. Take, for example, the succession in Scotland, and observe how each glacial 
epoch was preceded and apparently accompanied by partial submergence of the land : — 

1. Epoch of greatest mer de glace (lower boulder-clay) ; British and Scandinavian ice-sheets 

coalescent. Followed by wide land-surface = Continental Britain, with genial climate. 
Submergence of land — to what extent is uncertain, but apparently to 500 feet or so. 

2. Epoch of lesser mer de glace (upper boulder-clay) ; British and Scandinavian ice-sheets 

coalescent. Followed by wide land-surface = Continental Britain, with genial climate. 
Submergence of land for 100 feet or thereabout. 

3. Epoch of local ice-sheets' in mountain districts ; glaciers here and there coalesce on the 

low grounds; icebergs calved at mouths of Highland sea-lochs (moraines on 100-feet 
beach). Followed by wide land-surface = Continental Britain, with genial climate. 
Submergence of land for 50 feet or thereabout. 

4. Epoch of small local glaciers, here and there descending to sea (moraines on 50-feet 

beach). 



148 PROFESSOR JAMES GEIKIE ON THE 

These oscillations of the sea-level did not terminate with the emergence of the land 
after the formation of the 50-feet beach. There is evidence to show that subsequent to 
the retreat of the small local glaciers (4) and the emergence of the land, our shores 
extended seawards beyond their present limits, but how far we cannot tell. With this 
epoch of re-emergence the climate again became more genial, our forests once more 
attaining a greater vertical and horizontal range. Submergence then followed (25 to 30 
feet beach) accompanied by colder and more humid conditions, which, while unfavourable 
to forest growth, tended greatly to increase the spread of peat-bogs. We have no evi- 
dence, however, to show that small local glaciers again appeared. Finally the sea retired, 
and the present conditions ensued. 

It will be seen that the submergence which preceded and probably accompanied the 
advent of the lesser wrier de glace (2) was greater than that which heralded the appear- 
ance of the local ice-sheets (3), as that in turn exceeded the depression that accompanied 
the latest local glaciers (4). There would seem, therefore, to be some causal connection 
between cold climatic conditions and submergence. This is shown by the fact that not 
only did depression immediately precede and accompany the appearance of ice-sheets and 
glaciers, but the degree of submergence bore a remarkable relation to the extent of 
glaciation. Many speculations have been indulged in as to the cause of this curious 
connection between glaciation and depression ; these, however, I will not consider here. 
None of the explanations hitherto advanced is satisfactory, but the question is one well 
deserving the attention of physicists, and its solution would be of great service to 
geology. 

A still larger question which the history of these times suggests is the cause of 
climatic oscillations. I have maintained that the well-known theory advanced by James 
Croll is the only one that seems to throw any light upon the subject, and the observa- 
tions which have been made since I discussed the question at length, some fifteen years 
ago, have added strength to that conviction. As Sir Eobert Ball has remarked, the 
astronomical theory is really much stronger than Croll made it out to be. In his 
recently-published work, The Cause of an Ice Age, Sir Robert says that the theory is so 
thoroughly well based that there is no longer any ground for doubting its truth. " We 
have even shown," he continues, " that the astronomical conditions are so definite that 
astronomers are entitled to direct that vigorous search be instituted on this globe to 
discover the traces of those vast climatic changes through which astronomy declares that 
our earth must have passed." In concluding this paper, therefore, I may shortly indicate 
how far the geological evidence seems to answer the requirements of the theory. 

Following Croll, we find that the last period of great eccentricity of the earth's orbit 
extended over 1 GO, 000 years — the eccentricity reaching its highest value in the earlier 
stages of the cycle. It is obvious that during this long cycle the precession of the 
equinox must have completed seven revolutions. We might therefore expect to meet 
with geological evidence of recurrent cold or glacial and genial or interglacial epochs ; and 
not only so, but the records ought to show that the earlier glacial epoch or epochs were 



GLACIAL SUCCESSION IN" EUROPE. 149 

colder than those that followed. Now we find that the epoch of maximum glaciation 
supervened in early Pleistocene times, and that three separate and distinct glacial epochs 
of diminished severity followed. Of these three, the first would appear to have been 
almost as severe as that which preceded it, and it certainly much surpassed in severity 
the cold epochs of the later stages. But the epoch of maximum glaciation, or the first of 
the Pleistocene series, was not the earliest glacial epoch. It seems to have been pre- 
ceded by one of somewhat less severity than itself, but which nevertheless, as we gather 
from the observations of Pence and his collaborateurs, was about as important as that 
which came after the epoch of maximum glaciation. Hence it would appear that the 
correspondence of the geological evidence with the requirements of the astronomical 
theory is as close as we could expect it to be. Four glacial with intervening genial 
epochs appear to have fallen within Pleistocene times ; while towards the close of the 
Pliocene, or at the beginning of the Pleistocene Period, according as we choose to classify 
the deposits, an earlier glacial epoch, followed by genial interglacial conditions, super- 
vened. 

In this outline of a large subject it has not been possible to do mor,e than indicate 
very briefly the general nature of the evidence upon which the chief conclusions are 
based. I hope, however, to have an opportunity ere long of dealing with the whole 
question in detail. 



EXPLANATION OF PLATE. 

Map of Europe showing the areas occupied by ice during the Epoch of Maximum Glaciation (Second 
Glacial Epoch), and the extent of glaciation in Scandinavia, Finland, Baltic coast-lands, &c, and the British 
Islands during the Fourth Glacial Epoch. For the limits of the greater glaciation on the Continent, 
Habenicht, Penck, Nikitin, and Nathorst have been followed. The Great Baltic Glacier is chiefly after 
De Geer. 





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( 151 ) 



X. — On Some Eurypterid Remains from the Upper Silurian Rocks of the Pentland 
Hills. By Malcolm Laurie, B.Sc, F.L.S. (With Three Plates.) 

(Read 21st December 1891.) 

The Upper Silurian rocks of the Gutterford Burn, in the Pentland Hills, have for 
some time been known to contain Eurypterid remains,* but the fossils procured from these 
beds — chiefly owing to the exertions of Mr Hardy of Bavelaw Castle, and Mr Henderson, 
late Curator of the Phrenological Museum — have never been submitted to a thorough 
examination. When, therefore, by the kind permission of Sir E. Murdoch Smith, 
Director, and Dr E. H. Traquair, Keeper of the Natural History Collection in the 
Edinburgh Museum, I was given an opportunity of examining Mr Henderson's collec- 
tion, which was acquired by the Museum some years since, I entered upon the work 
with the expectation of finding some new and interesting forms which would repay 
description. My expectations in this respect have been more than fulfilled, as the collec- 
tion has yielded five undoubtedly new species, one of which I have made the type of a 
new genus. If to these one adds at least two other new species which are in the collec- 
tion of Mr Hardy of Bavelaw, and which I hope to have the pleasure of examining and 
describing at some future time, one is justified, I think, in saying that the Gutterford 
Burn is unequalled among Eurypterid localities with regard to the variety of forms it 
has yielded. Unfortunately the bed which has yielded these specimens is limited in 
extent, and further work on it would entail quarrying operations on a somewhat exten- 
sive scale. ' -• 

The rock in which the Eurypterids are preserved is an irregularly fissile fine-grained 
sandstone, containing a considerable amount of carbonaceous matter distributed in thin 
layers. The only other recognisable fossil which occurs in the rock is the so-called 
Dictyocaris Eamsayi, which occurs in considerable abundance. 

One point which has struck me in working at this collection is the large size of the 
eyes in most of the forms. The reason of this must be sought in the conditions under 
which they lived, and a comparison with recent forms would suggest deep water, but 
there is not sufficient evidence to make this more than a conjecture. 

I would like to take this opportunity of expressing my thanks to Dr Traquair, both 
for the permission to examine this interesting collection, and for the assistance he has 
given me throughout the work. 

Genus Stylonurus (H. Woodw.). 

This genus, which is characterised by " the peculiar form of the carapace, the great 

length of the telson or terminal joint, and the substitution of two pairs of long, slender, 

* Henderson, Trans. Edin. Geol. Soc, vol. iii. 
VOL. XXXVII. PART I. (NO. 10). 2 A 



152 MR MALCOLM LAURIE ON SOME EURYPTERID REMAINS FROM THE 

oar-like jaw-feet, instead of the single pair of broad, short, natatory organs more usually 
met with in this group,"' 5 " is represented by two species, both hitherto unknown to 
science. 

■ Stylonurus ornatus, n. sp. (PI. I. figs. 1-8.) 

This species is represented by fragments of three or four specimens which leave much 
to be yet ascertained as regards the exact proportions. 

The carapace, of which only the ventral surface is shown, is horseshoe-shaped, with 
a somewhat straight front margin. At its broadest point, which is about one-third of its 
length from the front end, it measures 150 mm., while at its posterior margin the breadth 
is only about 90 mm. In length it was probably about 150 mm. The anterior edge is 
bounded by a border 7 mm. in width, marked by 3 equidistant parallel lines. This border 
diminishes in breadth down the sides, and finally disappears about halfway down. Inside 
this border lies the inturned portion of the carapace, broad in front (32 mm.), but, like 
the border, narrowing down the sides, and disappearing close to the posterior edge of the 
carapace. A pair of curved lines run one on each side about 15 mm. from, and nearly 
parallel to, the margin of the carapace, approximating slightly to it along the anterior 
border. These lines approach to within 20 mm. of each other in front, and then bend 
abruptly, and run in a posterior direction to near the margin of the inturned portion. 
While the border appears to be free from any surface sculpture, this is far from being the 
case with the inturned portion. Down the sides where they are best shown, the sculp- 
ture consists of very fine scale-markings (fig. 3), with the convex side turned outwards 
towards the margin of the carapace. These markings do not extend to either boundary 
of the inturned portion, as they disappear some little way from the margin of the cara- 
pace towards the outer side, and towards the inner side are replaced by fine anastomosing 
lines, more or less longitudinal in direction. Within the inturned portion of the carapace 
the central space is occupied by the bases of the legs, but these are unfortunately not 
clearly enough shown to be accurately described. 

The eyes can be made out lying just within the inner margin of the inturned portion 
of the carapace, 34 mm. from the anterior margin, and about 31 mm. from the side. They 
appear to have been oval in form, the major axis, which lies at an angle of 45° to the 
axis of the body, measuring 18 mm. and the minor 10 mm. This is small in proportion 
compared with the eyes of some of the other members of the genus. 

The first six (mesosomatic) free segments are partly seen in fig. 1. Owing to less 
than half the segments being preserved, it is impossible to determine their width in this 
specimen. The length of the respective segments is as follows : — 1st, 16 mm. ; 2nd, 
18 mm. ; 3rd, 21 mm. ; 4th, 23 mm. ; 5th, 23 mm. ; 6th, 18 mm. The 5th segment thus 
shows no increase, and the sixth a slight diminution in length. The posterior margin of 
each segment in this specimen, which shows the ventral body wall, is bounded by a well 

* Woodward, Monograph of Brit. Fossil Crustacea, p. 122. 



UPPER SILURIAN ROCKS OF THE PENTLAND HILLS. 



153 



marked border or selvage, 4 mm. in breadth. The surface of these segments is covered 
with a very small inconspicuous ornamentation of the usual character. Down the right 
side of the specimen are seen what I take to be the plate-like abdominal appendages, 
between which and the body wall traces of branchial leaflets may be seen in the 3d and 
5th segments. The markings on these abdominal appendages are not shown in this 
specimen, but in the specimen which shows the central lobe of the genital plate, they are 
seen to have the form figured in fig. 4, the scales being rather angular, and giving the 
impression of zigzag lines running across the body. On the dorsal surface (fig. 2) a third 
type of ornamentation is met with, consisting of very broad (4 mm.) flat scales, in 
addition to which there is a single row of tubercles along the posterior margin of each 
segment. This variety of ornamentation in the one region of the body is worth noting 
as a warning against making species from fragments, the ornamentation on which is the 
only available character. 

The form of the central lobe of the genital plate is outlined in fig. 5. It differs 
very markedly from that figured by Dr Woodward in the restoration of S. Logani 
(Monograph, &c, p. 131), being long (36 mm.) and rounded at the end. Unfortunately 
the genital plates are not shown. 

The six posterior (metasomatic) segments and the beginning of the telson are only 
shown in one specimen (fig. 2). The figure represents the cast of the dorsal surface of 
these segments, certain portions being completed from the other half of the slab. The 
segments are crushed somewhat obliquely, and this makes the determination of their 
breadth very difficult, the following figures being only an approximation : — 



Segment. 






Width. 


Length. 


6th, . . 118 mm. 


20 mm 


7th, 






110 „ 


20 „ 


8th, 






94 „ 


23 „ 


9th, 






84 „ 


23 „ 


10th, 






78 „ 


25 „ 


11th, 






60 „ 


27 „ 


12th, 






42 „ 


• ... 


Telson, 






10 „ 


. 



These segments are all produced at the sides into curved " epimeral " pieces, which 
arise from the posterior corners of the segments. The posterior margins of the segments 
are ornamented by a single transverse row of slightly elongated tubercles, and the 
surface is covered, like that of the mesosoma, with large scale-markings. The last 
segment appears to be very short, with enormously expanded epimerites, and the 
markings on it are very much smaller than on the preceding ones. 

The Telson is attached between the large epimerites of the last segment, and is 
12 mm. in width. Unfortunately only a small portion of it is visible, and there is no 
clue to its probable length. Fig. 8 is one of two fragments of detached telsons which 



154 MR MALCOLM LAURIE ON SOME EURYPTERID REMAINS FROM THE 

probably belong to this species, though they differ from the usual form of telson in 
Stylonurus in tapering to a point. 

The metastoma is comparatively long and narrow, with a deep groove down the 
centre. The posterior margin is straight or slightly incurved, about 12 mm. in length, 
and ending in sharply rounded corners. The sides are slightly curved, and run almost 
parallel to each other. The anterior margin is not seen in any of the specimens^ 

The only appendages preserved are a pair of long narrow legs on each side, one of 
which is seen in situ in fig. 1, and another, the best of a number of detached fragments, 
is drawn in fig. 6. ' The bases of these limbs, one of which is outlined in fig. 7, appear 
to have been of about the same size, so that there would be two pairs of " ectognaths." 
They are similar in general shape to the ectognaths of Pterygotus or Slimonia, and bear 
five strong conical teeth along the biting margin. The postero-external angle is sharp 
and almost rectangular, and the surface, especially of the posterior part, is closely 
covered with angular scale- markings. The mode of attachment of the limb and the first 
joint of it are not shown. The five distal joints of the limb are marked by a strong 
longitudinal ridge. They decrease regularly in breadth, and vary considerably in length, 
the antepenultimate (5th) joint being the longest, a point in which they differ markedly 
from most other genera of fossil Merostomata. The measurements of the limb in fig. 7 



are as follows : — 






No. of Segment. 


Width. 


Length. 


3rd, 


18 mm. 


? mm 


4th, 


15 „ 


24 „ 


5th, 


11 „ 


40 „ 


6th, 


10 „ 


21 „ 


7th, 


8 „ 


20 „ 



The margin of the limb shows in places an obtuse crenulation (fig. 6a), and this probably 
existed along the whole length of the posterior margin. The penultimate joint bears a 
spine about 6 mm. long, inserted on the outer side of its articulation with the last 
segment. The last segment tapers to a point. No trace of ornamentation is seen on the 
appendages. 

This species, which I have ventured to name ornatus on account of the variety and 
abundance of the ornamentation, differs from S. Logani in size and in the form of the 
carapace, as well as in many minor points. The shape of the carapace and the position 
of the eyes distinguish it from most of the Old Eed Sandstone forms. From S. Powrei 
it differs further in the possession of epimera on the metasomatic segments and in the 
form of the limbs. 



Stylonurus macrophthalmus, n. sp. (PL II. figs. 9-11.) 

This species is considerably smaller than the preceding one, the length of the whole 
animal, minus the telson, being only 130 mm. The carapace is 37 mm. long and horse- 



UPPER SILURIAN ROCKS OF THE PENTLAND HILLS. 



155 



shoe-shaped, but does not narrow towards the posterior margin so markedly as in S. 
ornatus. The breadth at the widest portion, which is close to the front margin, is 40 mm., 
and at the posterior margin 35 mm. The margin is bounded in front by a narrow border 
(2 mm. wide), which runs out about half way down. A well developed ridge runs down the 
centre to within about 1 cm. of the front margin, and on each side of this are placed the 
prominences for the lateral eyes. These prominences are about half as long as the 
carapace (16 mm.), and about 10 mm. wide. The eye itself runs as a curved band, 
3 mm. broad, round the anterior and outer sides of the prominence. No trace of the 
occelli can be seen. The surface of the carapace is covered with a well marked, strongly 
curved scale ornamentation, and the posterior border is marked by a marginal row of 
elongated tubercles. 

The dimensions of the body segments are as follows : — 



1st, 


34 mm. wide. 


6 mm. long 


2nd, 


34 . 


6 


3rd, 


38 . 


8 


4th, 


38 


6 „ 


5th, 


38 


6 „ 


6th, 


. 32 „ 


6 „ 


7th, . 


30 


8 „ 


8th„ 


.. 27 „ 


9-5 „ 


9th, 


24 


10 


10th, 


• 22 „ 


11 „ 


11th, 


. 17? „ 


11-5 ,„ 


12th, 




. ... 



The segments thus diminish in width from the third, and increase markedly in length 
from the 7th on. The anterior segments show, a scale ornamentation very similar to 
that on the back of S. ornatus, but confined chiefly to the front portion of each segment. 
The posterior margin of each segment is marked by a row of tubercles, which are particu- 
larly conspicuous in the posterior segments. The last segment, and probably those 
preceding it, had epimera. 

The Telson (fig. 11) is not less than 52 mm. in length, but the point is unfortunately 
lost. It is 15 mm. wide at its point of attachment, and rapidly narrows to 5 mm., 
beyond which it tapers very gradually. It is deeply grooved by a pair of longitudinal 
furrows, and the median ridge between them is marked, by faint oblique denticula- 
tions. 

The Metastoma, the outline of which can be made out through the carapace (fig. 10), 
is 10 mm. wide at the posterior margin, which is straight, and becomes rapidly narrower 
towards the front. The front end of it is not visible. 

The limbs are only partly shown, but are very characteristic. On the right side 
(fig. 10) segments of the posterior limb are shown. The limb is very broad and short in 



156 MR MALCOLM LAURIE ON SOME EURYPTERID REMAINS FROM THE 

proportion to the rest of the animal, and is marked as usual in this genus by a longi- 
tudinal ridge. The dimensions, as far as they could be ascertained, are — 



9 mm. wide. 


10? long. 


6-5 


9 „ 


6-5 


13 „ 


4-5-5-5 . ,, 


• > ■ 



The 4th segment thus increases in width, while of the last segment only a small 
portion is seen. Fragments of a few joints of a second limb on this side can be made 
out, and seem about the same width as the posterior one. 

On the left side portions of two limbs are also seen. One shown in the cast (fig. 9) 
is very similar to the limb described on the right side, though differing slightly in size. 
The measure of the segments preserved is — 

11 mm. long. 6 mm. wide. 

17 „ 5 

9 5 „ 

Of the other limb on this side only the last 32 mm. are seen. It is peculiar in being 
very much narrower than those described above, the width being 2*5 mm. A longi- 
tudinal ridge can be made out, and the terminal joint, which is seen on both specimens, 
tapers to a point. If this limb corresponds to the anterior one on the right side it must 
taper very rapidly, and if not, then there is in this species a third limb rivalling the 
other two in length. The presence of this narrower limb, together with the size and 
position of the eyes and the shape of the metastoma, are sufficient to characterise this 
species, though the form of the carapace and the telson are also characteristic. 

Eurypterus (Dekay). 
This genus is represented by the remains of at least three distinct species. 

Eurypterus scorpioides (Woodward). 

Portions of four band-like sclerites, measuring when complete about 90 mm. in width 
and each 15 mm. in length, probably belong to this species. They are covered with 
punctate ornamentation, and each segment bears a pair of subcentral tubercles about 
1 *5 mm. in diameter and 6 mm. apart, which are rather nearer the posterior than the 
anterior margin of the segments. They must have belonged to a specimen somewhat 
smaller than that figured by Dr Woodward (Monograph, pis. xxix. fig. 1, xxx. fig. 9), 
but resemble his figure very closely both in the markings and in the presence of the pair 
of tubercles. 

The body and tail of a very large Eurypterus may be provisionally referred to this 
species, pending the discovery of further remains. It resembles the figure in Dr 
Woodward's Monograph (pi. xxix. fig. 1) in general form and in the nature of the 
markings, but exceeds it considerably in size. 



UPPER SILURIAN ROCKS OP THE PENTLAND HILLS. 



157 



Eurypterus conicus, n. sp. (PL II. figs. 12, 13 ; PL III. fig. 14.) 

This species is represented by a number of more or less complete specimens, the 
largest of which is about 150 mm. in length. 

The carapace is semicircular, but differs a good deal in different specimens owing to 
distortion. Fig. 14 is probably nearest to the original shape, and in this specimen it 
measures 28 mm. in breadth and 19 mm. in length. 

The dorsal surface is not seen, but the position of the eyes can be distinctly made 
out. They are large, 8 mm. in length, and somewhat oval in form, and about equidistant 
from the anterior and posterior margins of the carapace. The anterior ends of the eyes 
approach very close to the side of the carapace (1*5 mm.), but the posterior ends are 
slightly more distant. 

The metastoma is not seen, but the bases of the feet are very well shown. The last 
pair (" ectognaths ,T ) are broad and angular, the external angle being truncated parallel 
to the axis of the body for the attachment of the limb. The bases of four other pairs of 
postoral appendages can be made out, and also the position of the small and as yet 
undescribed chelicerse (fig. 14). 

The body in fig. 14, which I take to be the more normal form, the other being drawn 
out, tapers regularly from its point of attachment to the carapace to the telson, and the 
segments increase slightly in length. In fig. 12 the body is longer and narrower. The 
detailed measurements of both are as follows : — 



Fig. 14. 



Fig. 12. 



Segment. 

1. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

9. 
10. 
11. 
12. 
Telson, 



Len 


gth. 


Width. 


}« 




28 


mm 


mm. 


28 


» 


4-5 


» 


27 


» 


4 


j» 


25 


» 


4 


» 


24 


>i 


4 


» 


23 


» 


4-5 


n 


21 


;> 


6-5 


3) 


19 


» 


5 


yy 


16 


yy 


55 


*> 


14 


J* 


7 


» 


12 


9r 


7 


„ 


9 


it 


28 


?» 


5 


)> 



Length. 


Width. 


2-5 


mm. 


21 mm 


25 


» 


22 „ 


4 


?? 


22 „ 


4 


)> 


21 „ 


5 


j? 


20 „ 


5 


19 


19 „ 


4-5 


» 


17 „ 


7 


>> 


15 „ 


7 


)J 


? 


8 


J) 


12 „ 


8 


» 


10 „ 


11 


?) 


7-5 „ 


30 


>> 


5 „ 



Length of body, including carapace and telson — fig. 14, 105 mm. ; fig. 12, 121 mm. 
The posterior angles of the segments project slightly here and there, but there is no 
sign of regular epimera. 

The telson tapers regularly to a fine point. 

The genital plate is seen in fig. 12. The lateral plates are a good deal narrower than 



158 MR MALCOLM LAURIE ON SOME ETJRYPTERID REMAINS FROM THE 

the segment, and their outer ends are rounded. The median lobe is 7 mm. long and 
4 mm. wide at its base, and has a pointed angular form not common in this genus. 

Ornamentation of the ordinary kind is not shown on any part of the body, but fine 
anastomosing veins run over most of the surface. 

Only fragments of the limbs — of no value for descriptive purposes — are preserved. 

The form of the metastoma — slightly distorted — is shown in fig. 1 3. 

In the position of the eyes this form approaches most closely to E. lanceolatus (Salt.), 
(v. Woodwaed, pi. xxviii. figs. 1-3), but they are much larger in proportion. The form 
of the telson is somewhat more taper in this than in E. lanceolatus, and resembles most 
closely the fragments described by Salter as E. linearis* E. linearis, however, is 
considered by Schmidt! to be a synonym of E. Fischeri, a species very distinct from 
E. conicus. The form of the genital plate is also different from that of E. lanceolatus, 
but too little is known of the sexual variations of this structure for it to be of much value. 



Eurypterus cyclophthalmus, n. sp. (PI. III. fig. 15.) 

This species is represented by only one specimen, which shows the greater part of the 
carapace and portions of all the body segments. The carapace is semicircular in form, 
12 mm. long and 16 mm. wide at the posterior margin. It is bounded all round by a 
well marked narrow border (less than 1 mm. in width), and is destitute — as is the whole 
body — of scale-markings. The eyes are large (3*5 mm.), subcircular, and somewhat 
widely separated from each other (4*5 mm.). They are somewhat nearer the lateral than 
the anterior border of the carapace, and rather towards the front. Between the large 
eyes are a pair of small central eyes, which were probably placed on a prominence. 

The body increases in width to about the 3rd segment, and then decreases rapidly 
to the 7th, which is conical in form, and more gradually from the 7th to the end of the 
tail. The first six segments are short, the 7th very long, the 8th not so long as the 7th, 
and the succeeding ones about the same length as the 8th. The measurements may be 
tabulated as follows : — 



1st, 


1-8] 


nam. long. 






2nd, . 


2-5 


» 






3rd, . 


2-9 


» 






4th, 


3 


j> 






5th, . 


3 


)> 






6th, . 


33 


» ' 


7 


mm. wide 


7th, . 


4 


» • 


6 


» 


8th, . 


4-9 


» • > 


6 


» 


9th, . 


5 


» • < 


5 


» 


10th, . 


. U? 




4 


» 


11th, . 


» • • 


? 


>> 


12th, . 


. J 




? 


a 



The telson is not preserved, and there are only traces of the swimming feet. 
* Woodward, pL xxviii. figs. 10-12. t Schmidt, Mem. de I' Acad. Imp. d. 8c. de St. Petersbourg, vol. xxxi. p. 50. 



UPPER SILURIAN ROCKS OF THE PENTLAND HILLS. 



159 



This species seems sufficiently well characterised by the proportionate size, shape, and 
position of the eyes. Among the British species it approaches E. Brewsteri (Woodward, 
p. 151, pi. xviii. fig. 4) most nearly in the form of the carapace, but the eyes of 
E. Brewsteri are proportionately very small. In fact I know of no species except 
E. conicus, described above, in which the eyes are proportionately so large, and the 
difference of position of the eyes and the shape of the body render the two forms quite 
distinct. 

Drepanopterus, n. gen. 

Carapace broader than long ; widest about f ths from anterior margin. Body, 1st 
segment wider than posterior margin of carapace ; increases in width to 3rd segment, and 
then tapers rapidly. Limb elongated, sub cylindrical, terminating in a very slightly 
expanded joint, concave on posterior margin. 

This genus I have ventured to create for the reception of a single form, viz. : — 



Drepanopterus pentlandicua (PI. III. figs. 16, 17.) 

The carapace is horseshoe-shaped, the breadth at the widest part, which is about f ths 
of the length from the anterior margin, being 90 mm., and at the posterior margin only 
77 mm. The length of the carapace is only about 46 mm., the proportion between it 
and the breadth being about 4 to 7. The front margin is bent downwards, and there 
does not seem to have been a distinct border. The surface of the carapace, which is 
much crumpled, is covered with scale-markings, semicircular in form over the greater 
part, but along the sides becoming more angular, with the convexity directed outwards. 
The position of the eyes cannot be made out for certain, but they were probably placed 
at about 15 mm. from the front of the carapace, and 12 mm. from the side. 

The body, of which portions of nine segments are preserved, is broad and conical in 
form. The greatest breadth (96 mm.) is about the 3rd segment, and it narrows gradually 
in the region of the 4th and 5th segments, and more abruptly in the succeeding ones. 

The length and breadth of the segments is as follows : — 



1st, 


8 mm. long. 


77 mm. wide. 


2nd, , 


. 13 „ 


94 


3rd, . 


. 10 ■ „ 


96 


4th, . 


10 „ . 


94 


5th, . 


9 „ 


82 


6th, . 


9 „ 


64 


7th, . 


. 10 „ 


44 


8th, . 


. 11 „ 


36 


9th, . 


....,, . , 


27 , 



The 1st segment is very small in proportion, and seems to taper towards the sides, so 
that it does not appear along the margin. The 2nd and succeeding segments have their 
outer and posterior margins curved, and overlap from before backwards. Near the centre 

VOL. XXXVII. PART I. (NO. 10). 2 B 



160 



MR MALCOLM LAURIE ON SOME EURYPTERID REMAINS FROM THE 



of each of the first six segments is a comparatively large protuberance, somewhat 
elongated transversely, and the whole surface of the segments appears to have been 
closely covered with a minute, peculiar, and rather irregular marking, which, however, is 
only preserved in parts. 

The four distal joints of a limb (probably the last), measuring 94 mm. in length, are 
well shown, and differ from anything hitherto described among the Merostomata. The 
first three of these joints differ chiefly from each other in length. The first is ,33 mm. 
long, tapering, and slightly hourglass-shaped, the breadth at the proximal end being 
11 mm., in the middle 9 mm., and' at the distal extremity 10 mm. The second joint is 
27 mm. long, rather more tapering, and slightly concave on the posterior side. The 
third joint was much shorter (16 mm.), but is too much broken to allow its shape to be 
well made out. The last joint is 23 mm. long, and falcate in shape. The posterior 
margin is concave and evenly curved throughout its length, while the anterior margin 
runs for a short distance (5 mm.) approximately parallel to the posterior, and then curves 
strongly forward and sweeps round to meet the posterior margin at the pointed termi- 
nation of the limb. The breadth of this joint at its articulation with the preceding one 
is 7*3 mm., and at its broadest, which is 15 mm. along it, it measures 11 mm. 

The surface of the limb is covered with a punctate rather than scale-like marking. 
The marks are of two distinct sizes, the larger ones being distributed evenly at some 
little distance from each other, the space between them being occupied by the smaller 
ones. 

Traces of another limb, which must have equalled this one in breadth, are seen 
immediately in front of it at the side of the carapace, but they are too indistinct to 
admit of description. 

A small specimen (fig. 17) showing portions of the 3rd to 8th segments, with the 
whole of the 9th to 12th, and the telson, appears from the markings to belong to this 
species. The body in this specimen tapers rapidly to the 9th segment, and then more 
gradually to the 12th, the last four segments increasing in length as they diminish in 
width. The size of the segments, so far as it could be ascertained, is as follows : — 



3rd segment. 

4th 

5th 

6th 

7 th 

8th 

9th 
10th 
11th 
12th 
Telson 



3 ? 


mm. 


3 


)> 


25 


33 


'2 


» 


? 


» 


3 


» 


3 


J) 


4 


5) 


5-5 


>> 


17 


» 



? mm. wide. 

? 

? 

? 

? 

9 

8 

7 

5 

3 



The 12th segment is a truncated cone, narrowing from 5*5 mm. to 4'5 mm. 



UPPER SILURIAN ROCKS OF THE PENTLAND HILLS. 161 

The telson tapers regularly to a sharp point. The posterior portion of it is angular, 
with a sharp median ridge, but anteriorly this ridge expands into a flat triangular area. 

The proportion of this specimen to the one described above is roughly as 1 to 3, 
which would make the telson of the latter some 51 mm. in length and 9 mm. in breadth. 

If these posterior segments belong to Drepanopterus, they present a very close 
resemblance to those of some Eurypterids. The shape of the limb, however, and the 
proportions of the carapace, seem to me sufficiently distinctive to justify the formation 
of a fresh genus for the reception of this form. This genus would, as Mr Peach first 
suggested to me, occupy a position between Eurypterus and Stylonurus. The form it 
most nearly approaches in the shape of the appendage is that described by Hall * as a 
sub-genus of Eurypterus, under the name of Dolichopterus. Some specimens in Mr 
Hardy's collection will, I think, throw further light on the structure of this form. 



DESCRIPTION OF FIGURES. 

Plate I. 

Fig. 1. Portions of the carapace and anterior body segments of Stylonurus omatus. x £. 

Fig. 2. Posterior segments of the same species, x £.. 

Fig. 3. Portions of the ventral surface of the carapace, natural size, to show the sculpture. 

Fig. 4. Portion of the sculpture on the ventral surface, probably of the abdominal appendages, nat. size. 

Fig. 5. Outline of central lobe of genital plate, nat. size. 

Fig. 6. One of the elongated limbs, nat. size. 

Fig. 6a. Two joints of the same limb from the other half of the slab, to show the crenulated margin. 

Fig. 7. Outline of the metastoma and ectognath. nat. size. 

Fig. 8. Detached telson probably belonging to this species. x i. 

Plate II. 

Fig. 9. Cast of the most perfect specimen of Stylonurus macrophthalmus. n. sp., nat. size. 

Fig. 10. Carapace of the same specimen from the other half of the slab. nat. size. 

Fig. 11. Telson of St. macrophthalmus. nat. size. 

Fig. 12. Eurypterus conicus. nat. size. 

Fig. 13. Outline of metastoma of E. conicus. 

Plate III. 
Fig. 14. Eurypterus conicus. nat. size. 
Fig. 15. E. cyclophthalmus. nat. size. 

Fig. 16. Drepanopterus pentlandicus, carapace and greater part of body, with one limb. nat. size. 
Fig. 17. Posterior segments and telson of a smaller specimen of D. pentlandicus. nat. size. 

* Paleontology of Nevj York, vol. iii. p. 414. 



Trans Roy Soc. Edm p , Vol. XXXVII. 
M R Malcolm Laurie on Euripterids of Pentlands. — Plate i. 




M? Fat-lane &Erskine. Lith" Edin r 



Trans. Roy. Soc. Edm?, Vol XXXVII. 

M^MALCOLM LAURIE ON EURIPTERIDS OF PENTLANDS. Plate II. 











r i 



' — 




Fig. 10. 




Fig. 12. 




r\ 



Fig. 13. 



F^. 9. 




Fig. 11. 



M<Fa.rla.i.e JErsVrat LitlV Edir 



Trans Roy. Soc. Edm 1 ; Vol XXXVU 
M* Malcolm Laurie on Euripterids of Pentlands — Plate ln . 




Fig. 17. 



M'Farlane 4 Erskine. LitK! Edii 



( 163 ) 



XL 



—On Borolanite — an Igneous Rock intrusive in the Cambrian Limestone of Assy nt, 
Sutherlandshire, and the Torridon Sandstone of Ross-shire. By J. Horne, F.E.S.E., 
and J. J. H. Teall, F.R.S., of the Geological Survey. (Communicated by 
permission of the Director-General of the Geological Survey.) (With a Plate.) 



(Read 21st May 1892.) 



CONTENTS. 



PAGE 

I. Previous References to the Igneous Rocks 
associated with the Torridon Sandstone and 
Cambrian Strata in Assynt, .... 163 
II. Physical Relations of the Igneous Rocks intru- 
sive in the Torridon Sandstone and Cambrian 
Strata, 166 

1. Evidence in favour of their being intru- 

sive sheets, 166 

2. Horizons, 167 

3. Area of distribution, .... 167 

4. Date of intrusion, .... 167 
III. Intrusive Mass of Cnoc-na-Sr6ine, Loch Borolan 

and Ruighe Cnoc, 167 



1. Physical relations of this intrusive mass, 

and area of distribution, . 

2. Summary of the evidence regarding the 

geological relations of the mass, 

3. Area of the prevalent granitic type of 

Cnoc-na-Sr6ine, .... 

4. Area of the group of rocks included 

under Borolanite, .... 
IV. Petrological Description of Borolanite, 

1. Macroscopic characters of the rocks, 

2. Description of the minerals, . 

' '3. Microscopic characters of the rocks, 

4. Affinities of Borolanite, .... 



PAGE 

167 

170 

170 

170 
171 
171 
171 
175 
177 



The remarkable development of igneous rocks associated with the Torridon 
sandstone and Cambrian strata in Assynt, Sutherlandshire, forms one of the striking 
geological features of that region. In the various papers descriptive of the ancient 
sedimentary formations of the North- West Highlands by former observers, references are 
made to the lithological characters of these crystalline rocks and to their mode of 
occurrence. 

I. Previous References to the Igneous Rocks associated with the Torridon Sandstone and 

Cambrian Strata in Assynt. 

In 1856, Professor Nicol, in his paper " On the Red Sandstone and Conglomerate, 
and the Superposed Quartz-rocks, Limestones and Gneiss of the North- West Coast of 
Scotland," notes the occurrence of a bed of greenstone in the cliff of limestone to the 
south of the Inn at Inchnadamff.* He further states that in the area to the east of 
Ledmore, the relation of the quartzite to the gneiss bounding it on its eastern side was 
not visible on the line followed by him, as a mass of red felspar porphyry intervenes 
near Loch Borolan. 

In 1858, Sir Roderick Murchison, in his paper "On the Succession of the Older 
Rocks of the Northernmost Counties of Scotland, with some observations on the Orkney 
and Shetland Islands," refers to the band of red porphyry with large crystals of felspar, 
detected by Mr C. W. Peach and traced by him round the flank of Canisp, which is 
there interposed between the gneiss and the Torridon sandstone.t 



* Q. J. G. Soc, vol. xiii. p. 25. 
VOL. XXXVII. PART I. (NO. U> 



t Q. J. G. Soc, vol. xv. p. 365. 
2 C 



164 MR J. HORNE AND MR J. J. H. TEALL ON BOROLANITE. 

Again, in 1859, Murchison called attention to a band of syenitic greenstone, 
intercalated in the grey limestones at the bend of the road about a mile west from 
Inclmadamff. He states that it is from 40 to 50 feet thick, and as regularly bedded as 
the limestone both above and below it, though on examination it is seen to be a true 
igneous rock, containing crystals of hornblende with felspar and quartz. The indica- 
tions of contact alteration produced by this igneous mass had evidently attracted his 
attention, for he notes that the limestone above the igneous rock is more altered than 
that which lies beneath it, being in parts a crystalline marble.* 

In his brief summary of the igneous rocks of Sutherland, in the same communication, 
Murchison refers to an igneous rock of felspathic character, with some varieties, which, 
though termed porphyries, are rather syenites, breaking through the quartz-rocks far 
above the limestone of Assynt. These rocks spread out into large masses in the tract 
to the east of Assynt, which is traversed by the road to Oykel Bridget 

In 1860, Professor Nicol announced that, in the course of the previous year, he had 
observed that the Canisp porphyry not only breaks through the quartzite overlying the 
Torridon sandstone, but forms a mass more than a mile in diameter in the quartzite 
within a few hundred yards of the Inn at Inchnadamff. From these facts he inferred 
that the igneous intrusions must have been later than either the red sandstone (Torridon) 
or quartzite. J 

In 1882, Mr Huddleston referred to some of these igneous rocks in the Cambrian 
strata of Assynt, describing them as " a kind of diorite." 

In his various papers published in the Mineralogical Magazine from 1881 to 1884, 
Professor Heddle gave the results of his detailed examination of these rocks. He 
indicates the distribution of the Canisp porphyry, and speaks of it as one of the 
most striking porphyries of Scotland. He describes it as a structureless paste of a buff 
or dull brown colour, studded with crystals of a bright brick-red colour, commingled with 
others of a pale yellow ochre tint and with minuter ones of a dark green. He notes the 
occurrence of porphyritic crystals of orthoclase with albite and augite in the rock.§ 
Regarding the igneous rocks in the quartzites and dolomite in the neighbourhood of 
Inchnadamff, he refers to their distribution, and points out some of the lithological 
varieties, from the Canisp porphyry to the more basic types found in the limestone, in 
which hornblende is more abundant. IT Special reference is made to the remarkable 
" red porphyry " of Loch Borolan, and to the large area which it occupies from Ledbeg 
eastwards towards Kinlochailsh.** He takes exception to the name given to the rock of 
this hilly region, because no true porphyritic structure can be seen in it ; it has two 
ingredients, felspar and quartz, the former showing traces of crystalline form while the 
latter is frequently altogether absent. He defines the rock as a mass of agglutinated 
granules of a more or less brilliant red felspar. While indicating the localities of the 

* Q. J. G. Soc, vol. xvi. p. 221. § Min. Mag., vol. iv. p. 233 et seq. 

t Q. J. <1. Soc, vol. xvi. p. 232. T Min. Mag., vol. v. pp. 136 to 144. 

I Q. J. G. Soc, vol. xvii. p. 99. ** Min. Mag., vol. v. p. 144 and p. 295 et seq. 



MR J. HORNE AND MR J. J. H. TEALL ON BOROLANITE. 165 

marbles, he noted the important fact that they were all more or less adjacent to the 
mass of red felspar rock on Cnoc-na-Sr5ine or its branches, and he further made the im- 
portant deduction that the marble is merely a portion of the limestone series of 
Assynt.* But while giving weight to these observations, he was inclined to the opinion 
that the red rock of Cnoc-na-Sr5ine is a mere variety of the " Logan Rock." 

Near the south-western limit of the Cnoc-na-Sr5ine mass Professor Heddle observed a 
rock on the east bank of the Ledbeg River, at the bridge on the road leading to Elphin, 
about which he makes the following statement. The rock " is highly characteristic, 
though its characteristic features are possibly due to a modification of pseudomorphic 
alteration. In structure it resembles the westerly dull-red bed of ' Logan,' but it 
has a brown colour blotched with dull greenish-grey. It has a waxy lustre, is trans- 
lucent, and the greater part of it cuts easily with the knife. It consists of a muddy dull 
red felspar, in rude crystals, embedded in a substance which is identical in appearance 
with the pseudophite from Plaben Budweis." t 

Again, to the east of Aultivullin and Loch Am Meallan, he was impressed with the 
peculiar features of the rocks forming the main mass of borolanite. He observes that they 
are " in appearance intermediate between that of Cnoc-na-Sroine and the ' Logan Rock,' 
with here and there a great resemblance to the rock seen at the Bridge of Ledbeg ; at 
other points there is some slight resemblance to an igneous rock. The rock of the east 
end of the hill is again like ' Logan,' of a red hue, and a grey-brown labradorite-like 
bed is the last seen." J 

In 1883, Dr Callaway made brief allusion to some of the igneous rocks in the 
Assynt series, referring more particularly to the Loch Ailsh group, extending from 
Ledmore to the gap south of Loch Ailsh. While noting the granitoid texture which is 
characteristic of this mass, he called attention to an exceptional garnetiferous variety 
occurring to the east of Loch Borolan, on the slope north of the road.§ In the appendix 
to this paper, Professor Bonney describes the microscopic characters of a few specimens 
of these igneous rocks, collected by Dr Callaway. IF Regarding the exceptional garneti- 
ferous variety, he states that it is " a most perplexing rock. In the slide a fair quantity 
of black mica is at once recognised, and a number of subtranslucent sap brown garnets, 

the larger (being the less regularly formed), including flakes of mica, &c The 

ground of the slide appears to consist partly of a felspar, in patches of a most irregular 
form (with perhaps a little quartz), and a mineral which occurs in rather wavy bunches, 
like tufts of long thread or rootlets, or a kind of ' canal system.' It seems to have re- 
placed the felspar, and may be one of the fibrolite group." 

One of the dykes in the Traligill Burn near Inchnadamff is described by Professor 
Bonney as a hornblende porphyrite. 

In 1886, one of the authors of this paper published notes on some hornblende-bearing 
rocks from Inchnadamff, containing a description of the rocks and the characters of the 

* Min. Mag., vol. v. p. 274. + Mineralog. Mag., vol. v. p. 294. % Mineralog. Mag., vol. v. p. 295. 

§ Q. J. G. Soc, vol. xxxix. p. 409. IT Q. J. G. Soc, vol. xxxix. p. 420. 



166 MR J. HORNE AND MR, J. J. H. TEALL ON BOROLANITE. 

rock-forming minerals.* He indicated some of the remarkable lithological varieties of 
these intrusive rocks, and gave analyses of three specimens, viz. : — 1. Hornblende porphy- 
rite, intrusive in quartzite ; 2. Porphyritic diorite ; 3. Plagioclase — pyroxene — hornblende 
rock near Inchnadamff, intrusive in limestone. The last, which is the most basic, differs 
from the others in containing a large amount of colourless pyroxene. The author suggested 
that "in all probability the pyroxene is a nearly pure lime-magnesia bisilicate, and one is 
tempted, therefore, to ask whether it may not be due to the absorption by the igneous magma 
of a certain amount of the dolomitic limestone into which the rock has been intruded." 

In 1888, in the report on the recent work of the Geological Survey in the North- 
West Highlands of Scotland, special reference was made to the intrusive igneous rocks 
associated with the Torridon sandstone and Cambrian strata in Assynt, brief descriptions 
being given of the geological features which they present in the field, t 

II. Physical Relations of the Igneous Rocks intrusive in the Torridon Sandstone and 

Cambrian Strata. 

1. Before proceeding to the description of the particular group of rocks that form the 
subject of this communication, it may be desirable to refer generally to the physical 
relations which the igneous materials, as a whole, present in the field. Perhaps their 
most characteristic feature is their occurrence in the form of intrusive sheets injected 
along the planes of bedding of the sedimentary strata. The remarkable parallelism of 
the igneous bands, varying in thickness as a rule from 10 to 50 feet, and the manner in 
which they cling to the same horizon for considerable distances, have led one or two 
observers to the conclusion that they are contemporaneous lava flows. But a careful exam- 
ination of the physical relations of these igneous rocks reveals certain phenomena which 
are characteristic of intrusive sheets. First, when the igneous bands are traced along 
the line of outcrop, they pass transgressively from lower to higher members of the same 
group, and occasionally plunge downwards into a lower platform. A striking example of 
these phenomena is to be found on the western face of Canisp, where a mass of porphy- 
ritic felsite rises from the old platform of Archaean gneiss, passing upwards into the 
overlying Torridon sandstone and eventually spreading along the bedding planes. Second, 
where the sheets reach a considerable thickness, both the overlying and underlying 
strata are altered by contact metamorphism. The zone of marble surrounding the great 
igneous mass to the east of Ledbeg admirably illustrates this local metamorphism, and 
even in the case of the thinner sheets, the quartzites are hardened and welded to the 
igneous rock. Third, there is a marked absence of cellular structure in the various types 
of igneous materials. Fourth, they occasionally contain fragments of the sedimentary 
rocks which they traverse. 

* Notes on some hornblende-bearing rocks from Inchnadamff. J. J. H. Teall, Geol. Mag., 1886, p. 346. 

t " ['i [i i' "ti the Recent Work of the Geological Survey in the North-West Highlands of Scotland, based on the 
Field Notes and Maps of Messrs B. N. Peach ; J. Horne ; W. Gunn ; C. T. Clough ; L. Hinxman and H. M. Cadell," 
Q. J. G. Soc, xliv. p. 378. 



MR J. HORNE AND MR J. J. H. TEALL ON BOROLANITE. 167 

2. The detailed mapping of the region has also shown that these igneous intercala- 
tions are more or less confined to certain definite horizons in the sedimentary strata. 
Several sheets are interleaved in the Torridon sandstone, which rests unconformably on 
the eroded platform of Archaean gneiss, while in the overlying Cambrian strata, two 
occur in the basal quartzites, two in the " Pipe-Eock," one in the " Fucoid Beds," two in 
the lowest group of limestone, and one in the succeeding group of Eilean Dubh limestone. 
These intrusive masses are not always traceable, some of the bands being much more con- 
stant than others, but in the area surrounding Inchnadamff they are typically developed. 

3. It is rather remarkable that this outbreak of volcanic activity in these ancient 
sedimentary systems is comparativ elylocal, for though the Torridon sandstone and the 
overlying Cambrian strata can be traced continuously for a distance of 90 miles across the 
counties of Sutherland and Eoss, the igneous rocks are confined to a limited portion of 
this belt. In the area lying to the west of the post-Cambrian terrestrial movements, 
they extend from Loch Assynt to near Elphin — a distance of about nine miles, but in the 
region affeeted by these movements they stretch from Glencoul to Ullapool — a distance 
of 24 miles. Originally they must have penetrated far to the east, for they are 
carried westwards with the associated sedimentary strata along the higher thrust-planes. 

4. From the fact that the intrusive sheets are truncated by the numerous thrusts or 
lines of displacement traversing the region, it is obvious that the period of volcanic activity 
to which they belong is later than the Cambrian limestone of Durness and older than 
the post-Cambrian movements. 

III. Intrusive Mass of Cnoc-na-Srdine, Loch Borolan, and Ruighe Cnoc. 

1. In the southern portion of Assynt, there is a remarkable development of these in- 
trusive igneous rocks, covering an extensive area from Ledbeg eastwards to a point near 
the road leading to Loch Ailsh — a distance of 5 miles. They can also be traced from 
the peat-clad moor south-east of Loch Borolan northwards to the slopes of Sgonnan 
M5r. The particular group of rocks which are specially described in this paper are 
associated with this great intrusive mass. # 

The relations of this extensive series of igneous rocks to the surrounding strata are of 
special interest and in the neighbourhood of Ledbeg and Ledmore are rather complicated. 
In the latter region there are various outliers of materials lying above the Ben More 
thrust-plane, originally continuous but now occurring in isolated patches, which cover 
alike portions of the igneous rocks and the adjacent marble. Notwithstanding these 
complications, there are several sections defining the limits of the intrusive rocks and 
their relations to the altered Cambrian limestone. 

Between Ledbeg and the road leading to Loch Ailsh the eruptive rocks form a range 
of hilly ground rising to a height of 1305 feet in Cnoc-na-Sr5ine. From Loch Borolan to 

* The description of the physical relations of this intrusive mass may be more readily followed by referring to Sheet 
101 (one-inch) of the Geological Survey Map of Scotland. 



168 MR J. HORNE AND MR J. J. H. TEALL ON BOROLANITE. 

Ledbeg they have been so denuded as to present a prominent escarpment skirting the 
road leading to Inchnadamff. But this conspicuous crag is by no means the western 
limit of the mass. 

Ascending the Ledbeg River from the point where it joins the Ledmore River, 
| of a mile east of Cama Loch, the coarse granitic rock is exposed at various points 
in the stream section. About 70 yards to the south of Ledbeg Cottage the marble is 
visible, and further up the stream, at the ford leading to the cottage, the basal bands of 
the Durness limestone are met with in a highly altered form. A few yards to the west 
of the river, and immediately to the north of the cottage, one of the bands of serpulite 
limestone at the base of the Grudaidh group is clearly recognisable, though considerably 
metamorphosed. Returning to the river, and following the section to a point about 200 
yards above the footbridge, there are several excellent exposures of the granitic rock 
penetrating the marble on both banks of the stream. Indeed the site of the old quarry 
where the marble was formerly wrought is close by this locality, being situated a few yards 
to the east of the river and near the road to Inchnadamff. The evidence that the marble 
is merely an altered portion of the Durness limestone is still further strengthened by the 
occurrence of recognisable bands of the basal limestone in an altered form, in a tributary 
of the Ledbeg River, about 500 yards to the north of Ledbeg Cottage. Our colleague, 
Mr Peach, who mapped this portion of the Ledbeg River, has traced the marble at 
intervals from Ledbeg westwards to a point high up on the slope of Cnoc-an-Leathaid- 
Beg, where it is associated with the pink granitic rock. At the latter locality the 
marble and the intrusive granitoid rock are alike buried underneath the basal quartzites 
and the " Pipe-Rock," resting unconformably on a slice of Lewisian gneiss. These 
materials form an outlier separated by denudation from the displaced masses lying 
above the Ben More thrust-plane. 

On the south side of the Ledbeg River, due south of the shepherd's house at Loyne, there 
is another small outlier of shattered basal quartzite, separated by a powerful thrust-plane 
from the underlying materials. Measuring about 700 yards in length and about 400 
yards in breadth, these displaced quartzites rest partly on thrust " Fucoid Beds," 
serpulite grit and basal limestone, and partly on the marble. Along the eastern limit of 
this outlier a line of swallow holes can be traced, and the marble is visible in a 
conspicuous grassy patch of ground adjoining the basal quartzites about 500 yards to the 
south of the river. Crossing the flat peat-covered ground to the south of this exposure, 
the marble is again seen in a small rocky knoll within 50 yards of the boundary line of 
the granitic mass of Cnoc-na-Sr6ine. From the latter point the boundary line of the 
igneous rocks sweeps eastwards along the southern slope of the valley to the base of 
Ruighe Cnoc, where there is a fine escarpment of the pink granitic rock. For most 
of this distance the junction of the intrusive mass with the thrust Cambrian strata is 
buried under peat and drift. 

But on the north side of the valley, about 150 yards to the north-east of the Loyne 
shepherd's house, there is a detached mass of the pink orthoclase rock of Cnoc-na-Sr5ine in 



MR J. HORNE AND MR J. J. H. TEALL ON BOROLANITE. 169 

immediate contact with the marble. An excellent section of the igneous rock is exposed 
in a small tributary of the Ledbeg River, showing the intrusive mass penetrating the 
marble. The altered limestone can be traced from the northern limit of this igneous rock 
for a distance of about 150 yards to the base of Ben Fuarain, where it is covered by 
crushed Torridon sandstone. Here again a gradual passage is observable from the white 
crystalline marble into the white limestone of the Eilean Dubh group. The crushed and 
shattered Torridon sandstone, overlying the marble and unaltered Durness limestone, 
rests unconformably on Lewisian gneiss, and both are covered in turn by the basal 
quartzites and a small portion of the " Pipe-Rock." All these materials, viz., the gneiss, 
the Torridon sandstone and Cambrian quartzites, are separated from the underlying 
limestone by a complete discordance. They form one of the most interesting of the 
numerous outliers of displaced materials resting above the Ben More thrust-plane. 

Proceeding to the south-west slope of Sgonnan Mor, several sections of special interest 
are met with, revealing the relations of the igneous mass to the surrounding strata. On 
this declivity four small streams unite to form an important tributary of the Ledbeg 
River at Luban Croma. In each of these burns the intrusive rock is visible, and in the 
two most northerly there are excellent sections showing peculiar types of the igneous 
mass penetrating the marble between the 1000 feet and 1250 feet contour lines. Not far 
above this level, both the marble and the intrusive rock are abruptly truncated by the 
Ben More thrust-plane bringing forward a slice of Archaean rocks covered unconformably 
by the Torridon sandstone and Cambrian strata. On the south-west slope of this 
mountain, the Torridon flags, shales and grits overlie in inverted order the igneous rock 
and the marble, for as we ascend the slope the strata have a persistent easterly dip till 
we reach the coarse conglomerate at the base of the Torridon sandstone, in contact with 
the overlying Lewisian gneiss and its basic dykes. 

The ground between Sgonnan Mor and Kinloch Ailsh has not been surveyed in 
detail, but from certain traverses across the area it seems apparent that the intrusive 
igneous rocks reappear at certain localities with the displaced materials overlying the Ben 
More thrust-plane. 

In the neighbourhood of Strath sheaskich near Loch Ailsh the eastern limit of the 
intrusive mass can be approximately defined by means of rocky knolls projecting through 
the peat and drift. It is bounded by massive white marble, apparently resting on the 
igneous rock, and dipping towards the east at angles varying from 30° to 70°. This 
junction line can be traced through the gap, close by the Kinloch Ailsh road to the 
high road leading to Inchnadamff. 

The southern limit of this great intrusive mass is to a large extent obscured by the 
extensive covering of peat stretching continuously from the Kinloch Ailsh road westwards 
to Loch Urigill and Ledmore. But occasional exposures of rock are to be found in the 
streams cutting through the peat and drift. It extends far to the south of the road 
between Loch Borolan and Aultivullin, for it is visible in small burn sections about three- 
quarters of a mile due south of Aultivullin. Here again it is overlapped by the Cambrian 



170 MR J. HORNE AND MR J. J. H. TEALL ON BOROLANITE. 

quartzites and Lewisian gneiss lying above the Ben More thrust-plane. The marble is 
found along the north-east shore of Loch Urigill, about a mile to the south of Loch 
Borolan, and it is therefore probable that the igneous mass extends for some distance 
southwards from the latter loch. 

Excellent sections are visible along the banks of the Ledmore River from Loch 
Borolan to the point where it is joined by the Ledbeg tributary. Immediately to the 
south of the junction of these two streams there are small exposures of those peculiar 
types of the igneous rocks, which are specially described in this paper, laid bare by the 
denudation of the adjacent quartzites and gneiss overlying the Ben More thrust-plane. 

2. Summarising the foregoing evidence regarding the physical relations of the 
great Loch Borolan igneous mass, it is evident (1) that a zone of crystalline marble can 
be traced for long distances in immediate contact with or close to the eruptive rock, (2) 
that a gradual passage can be followed at certain localities from the marble into 
recognisable bands of the Durness limestone, (3) that on the slopes of Sgonnan M6r and 
again at Cnoc-na-Glas-Choille the intrusive mass is truncated by the main outcrop of 
the Ben More thrust-plane, (4) that in the neighbourhood of Ledmore, Ledbeg and Loyne, 
outliers of the materials overlying the Ben More thrust-plane cover portions of the 
intrusive rock and the altered Cambrian strata, (5) that from the apparent superposition 
of the marble along the eastern limit of the igneous mass, it is not improbable that the 
latter may resemble the other intrusive sills in Assynt, and may have been originally 
injected as a great sheet along the bedding planes. 

3. Throughout this extensive area, there are striking lithological differences in the 
character of the eruptive rocks. The prevalent type in the western portion of the mass 
along the ridge extending from Cnoc-na-Sr5ine eastwards to Lochan Sgeirach is a coarse 
granitic rock consisting mainly of orthoclase with a little quartz. Occasionally large 
porphyritic crystals of orthoclase are developed and mica is sometimes present. 

4. But immediately to the east of Loch Borolan, and about three-quarters of a mile 
to the east of Aultnacallagach Inn, the rock assumes a different phase. Dark brown and 
black garnets are associated with the orthoclase and a peculiar blue mineral to be 
referred to presently. The rock is massive, of a greyish or pink tint, unfoliated, and 
effervesces freely with acid. This type is well developed on the rocky knolls to the 
north of the road on the slope named Am Meallan on the 6-inch Ordnance Map. 

Not far to the east of this locality there is a small stream (Aultivullin) draining 
Loch-a-Mheallain and flowing southwards into the Allt Lon Dubh, situated about a mile 
and a half to the east of Aultnacallagach Inn. Another striking variety is exposed in 
this burn section above the waterfall. This type is distinctly foliated, with white knots 
and abundant black garnets set in a dark grey matrix. The dip of the foliation planes 
is towards the east at an angle of 15°. On the hill slope to the east of this stream and 
Loch-a-Mheallain this foliated variety of borolanite is conspicuously developed, but the 
foliation disappears as we pass eastwards towards the limit of the mass. Following the 
high road from Aultivullin for about half a mile to the east of that locality, the unfoliated 



MR J. HORNE AND MR J. J. H. TEALL ON BOROLANITE. 171 

type of this rock is exposed in knolls by the side of a small stream. The rock is dark 
grey, with abundant white knots and black garnets, effervescing very freely with acid. 
The foliated and unfoliated varieties just referred to are traceable at intervals in the 
stream sections to the south of Aultivullin as far as the slope of Cnoc-na-Glas-Choille. 

These exceptional varieties to which special attention is called in this paper have been 
traced across an area upwards of two miles in length from Loch-a-Mheallain to Cnoc-na- 
Glas-Choille, and about a mile in breadth from east to west. 

But, in addition to these localities, abnormal types which will be referred to on a 
subsequent page occur not far to the south of the junction of the Ledmore and Ledbeg 
Rivers, and also at the base of the north-west slope of Cnoc-na-Sr5ine. At the latter 
locality it forms the margin of the igneous mass, and the marble occurs not far distant 
on the south bank of the Ledbeg River, about half a mile to the east of the Loyne 
shepherd's house. 

But perhaps the most interesting sections showing the relation of this peculiar 
type of rock with the pink and white knots to the marble, occur in the small streams on 
the south-west slope of Sgonnan Mor. 

IV. Penological Description of Borolanite. 

1. The prevailing type is a medium-grained rock of a dark grey colour. It frequently 
contains whitish or pinkish patches, usually more or less spherical or ellipsoidal in form, 
but occasionally showing polyhedral boun- 
daries. These patches vary considerably in 
size. The smallest are only just distinctly 
visible to the naked eye ; the largest measure 
an inch or more across. They also vary con- 
siderably in relative abundance. Sometimes 
they are absent altogether, whereas at other 
times the main mass of the rock is composed 
of them. The general appearance of a 
polished surface is represented in fig. 1. 

Where the rock has been subjected to ,.„,,,.-,«■,_,„. 

J Fig. 1. — About Two-thirds Natural Size. 

deformation during or subsequent to consoli- 
dation, the white patches take the form of lenticles or streaks, as may be seen in fig. 2. 

2. The principal interest of these rocks centres in their peculiar mineralogical 
composition. The dominant constituents are orthoclase, plagioclase, a substance which 
gelatinises with hydrochloric acid, melanite, pyroxene and biotite. The small black 
spots seen in fig. 1 are due to the garnet. Apatite, sphene and iron ores occur as 
accessory constituents. The secondary products include a peculiar blue substance which 
is probably an alteration product after a mineral of the sodalite group, white mica and 
possibly calcite. Many of the specimens effervesce freely with acid, but this is probably 

VOL. XXXVII. PART I. (NO. 11). 2 D 




172 



MR J. HORNE AND MR J. J. H. TEALL ON BOROLANITE. 



due rather to the introduction of carbonates from the surrounding limestone than to their 
development by the decomposition of the rock. 

Nepheline almost certainly occurred as an original constituent of some varieties, but 
is now only represented by decomposition products. Wollastonite is present as the 
principal constituent of certain inclusions occurring in a specimen from the south side 
of Sgonnan M5r. 

Orthoclase enters largely into the composition of all the rocks, and is found also in 
certain veins. Tested by Szabo's method, the felspar of the rock appears to be identical 
with that of the veins. The flame-reaction is that of an orthoclase fairly rich in soda. 




Fig. 2.— About Half Natural Size. 

The specific gravity is about 2*52. The felspar of the veins is of a purplish-brown colour, 
and the individuals often measure an inch across. The two cleavages are easily 
recognisable, but the basal cleavage is much the more perfect of the two. The reflections 
from the basal cleavages are bright, those from the clino-pinacoid dull. The individuals 
are tabular, with conspicuous development of the clino-pinacoid. Flakes parallel to 
M {010} give extinction angles of 6° or 7° referred to the trace of the P {001} cleavage. 
Those parallel to P sometimes give straight extinction and sometimes an indefinite 
extinction due to different portions extinguishing in slightly different positions. In the 
M-flakes the emergence of a positive bisectrix is seen in convergent light, and the 
position of the optic axial plane can be proved to be that of normal orthoclase. The 
twinning, when it occurs, is on the Carlsbad plan. In the massive varieties the 
orthoclase occurs, as a rule, in large, allotriomorphic grains, forming, as it were, the 
groundmass of the rock, the other minerals being present in it as inclusions. In the 
foliated varieties it forms granulitic aggregates. Orthoclase forms a large portion of the 
white spots, where it is often micro-pegmatitically intergrown with a substance which is 
probably an alteration product after nepheline. 

Striated or plagioclase felspar is comparatively scarce and is entirely absent from 
many varieties. It occurs as small irregular grains between large individuals of 
orthoclase, as grains in association with similar grains of orthoclase, and also as a 



MR J. HORNE AND MR J. J. H. TEALL ON BOROLANITE. 173 

constituent of microperthite. In one specimen fairly large individuals without any 
very definite crystallographic boundaries were observed in a fine-grained groundmass of 
biotite and orthoclase. 

Next to orthoclase, melanite is the most important constituent of these singular rocks. 
It is black, and possesses, when broken, a somewhat resinous lustre. Good crystalline 
form is absent, as a rule, but perfect little crystals may occasionally be observed. The 
dominant form is the rhombic dodecahedron {HO}. The edges of this form are 
sometimes truncated by those of the icosi-tetrahedron {211}, exactly as is the case in the 
well-known melanite from Frascati. The mineral fuses in the flame of the blow-pipe 
to a black glass which is slightly magnetic. In thin sections the colour of the 
melanite is seen to vary from a pale to a deep brown (see fig. 1, PL XXXVII.). The central 
parts of an individual are sometimes more deeply coloured than the marginal parts, 
and sometimes the reverse relation may be observed. The borders of the differently 
tinted portions may correspond to the crystallographic outline of the individual, thus 
producing true zonal structure, or they may be irregular. 

The individuals vary in size from very small grains, only "05 mm. in diameter, to 
large crystals or irregular masses measuring 1 or 2 mm. across. Melanite is both 
idiomorphic and allotriomorphic with respect to felspar. Iron-ores, sphene and biotite 
occur as inclusions. 

The biotite appears black when viewed microscopically. Cleavage flakes, examined 
with the microscope, appear a dull dark green by transmitted light, and are nearly 
uniaxial. Thin sections at right angles to the principal cleavage change from dark green 
to yellowish brown as the stage is rotated over the polariser. The individuals vary 
considerably in size and are generally irregular in form. The larger flakes are often 
corrugated. Pyroxene, iron-ores, garnet and occasionally felspar, occur as inclusions. 

The pyroxene is green both by reflected and transmitted light. It is quite 
subordinate in quantity, as a rule, to the orthoclase and melanite. In one specimen from 
the north-west slopes of Cnoc-na-Sr5ine and in another from the burn close to the marble 
at Ledbeg it occurs abundantly, and makes with felspar the bulk of the rock. Melanite 
is absent from these specimens. As a rule, the mineral is without any very definite 
crystalline form, but sometimes the individuals are elongated in the direction of the 
vertical axis and more or less idiomorphic in the prismatic zone. The forms recognisable 
are {110}, {010} and {100}. The prismatic faces {110} are not uniformly developed in 
the different crystals ; sometimes they appear only as slight truncations and sometimes they 
are developed almost to the exclusion of the clino-pinacoid. The ortho-pinacoid is always 
conspicuous when any trace of form is present. As already stated, the mineral appears 
green in thin sections, but the tint is not uniform — the marginal portions being often 
more deeply coloured than the central parts. There is also a faint pleochroism. The 
least axis of elasticity makes an angle of about 40° with the vertical axis of the crystal. 
All the above characters agree with those of pyroxenes known to occur in nepheline- 
bearing rocks. Magnetite and apatite are present as inclusions. 



174 



MR J. HORNE AND MR J. J. H. TEALL ON BOROLANITE. 



Sphene is by no means uniformly distributed in the different varieties. In the 
specimen from the north-west slopes of Cnoc-na-Sr5ine, to which reference has already 
been made, it occurs in large ophitic plates which are allotriomorphic with respect to 
felspar and pyroxene. In the melanite-bearing rocks sphene is frequently present in 
the form of minute ('03 x '07 mm.) and often spindle-shaped granules. These granules 
are found only in the garnet. They sometimes occur so abundantly as to leave scarcely 
any of the isotropic garnet -substance between them in the thin sections. At other times 
they are entirely absent. That they are sphene is proved by the fact that they possess 
the refraction, double-refraction, colour, pleochroism and dispersion of this mineral. 

Apatite is present in the form of stout hexagonal prisms. It is always perfectly 
fresh, and may occur as inclusions in any of the other constituents. In one exceptional 
specimen from the burn at Ledmore it is present in great abundance. This specimen is 
a black, coarsely crystalline rock composed of pyroxene, melanite and apatite, with a 
little biotite and pyrite. 

Magnetite is sparingly present in many of the rocks. It occurs as grains which may 
be readily extracted from the powder of the rock by means of a weak magnet. 

The felspar of these rocks is frequently associated with a turbid substance giving 
indefinite optical characters. In one or two instances this substance shows hexagonal (see 
fig. 5, PI. XXXVII.) and rectangular sections. As a rule, it either forms mi cro-pegmatitic 
aggregates with felspar, or occurs in patches with no suggestion of crystalline form. On 
treating a slide or a cut surface of the rock with hydrochloric acid, little protuberances of 
gelatinous silica mark the distribution of this substance. The acid solution contains 
soda in abundance.* 

It seems impossible, therefore, to avoid the conclusion that nepheline occurred as an 
original constituent of these rocks. This conclusion is strengthened by the fact that 
melanite and green pyroxenes are well-known associates of nepheline and leucite. 

A peculiar blue substance occurs wedged in between the large individuals of 
orthoclase in certain veins, and is found also as a constituent of some of the white spots. 
It shows aggregate polarisation, and is decomposed by hydrochloric and sulphuric acids, 
with the separation of gelatinous silica and the evolution of bubbles. 

After adding water to the hydrochloric acid solution and evaporating slowly, salt and 
gypsum crystals are developed — the former in great abundance. A partial analysis was 
made on about half a gramme of this substance, with the following result : — 



Silica, 

Alumina, 

Lime, 

Potash, 

Soda, 

Sulphuric anhydride, 

Sp. Gr., 



2-41-2 



43. 



36-1 

28-4 

3-2 

1-8 

16-2 

5-9 

916 



* Proved by the uranium-acetate test. 



MR J. HORNE AND MR J. J. H. TEALL ON BOROLANITE. 175 

Water and carbonic acid are present, but were not determined. The reaction of this 
substance with acid is suggestive of cancrinite, but the occurrence of sulphuric acid 
points to the conclusion that it is an alteration product after a mineral of the sodalite 
group. 

Wollastonite was found only as a constituent of certain inclusions in a specimen col- 
lected on the south side of Sgonnan Mdr. These inclusions are of a greenish white colour. 
When examined with a lens they are seen to consist mainly of a colourless mineral 
having a pearly lustre and a fibrous structure. This mineral is decomposed by hot 
hydrochloric acid, and the solution, after the addition of dilute sulphuric acid, yields 
gypsum crystals in abundance. Its specific gravity is 2*895. By detaching a small 
fragment and crushing it upon a slide, numerous long fiat laths are obtained. These 
invariably give straight extinction. When examined in convergent polarised light they 
fall into two groups : — (a) Those which show the emergence of an optic axis near one 
margin of the field of view and that of a bisectrix on the opposite margin ; (6) those 
which show the emergence of an optic axis nearly in the centre of the field of view. 
Observations on flakes of the first group prove that the optic axial plane is at right angles 
to the length of the flakes, and that the minor axis of depol'arisation is parallel to the 
length. We may, therefore, infer that the acute bisectrix is the least axis of elasticity 
and that the double-refraction is positive. All these facts point to the conclusion that 
the mineral is wollastonite. The flakes above referred to are determined by the two 
dominant cleavages. The straight extinction is a consequence of the fact that the edge 
formed by the meeting of the two principal cleavage planes is at right angles to the plane 
of symmetry of the monoclinic mineral, and coincident, therefore, with the mean axis of 
elasticity.* 

The greenish tinge of the aggregates of wollastonite is due to the presence of a large 
number of extremely minute granules of green pyroxene. It is interesting to note that 
the aggregates of wollastonite from Willsburg, N.Y., U.S.A., also contain grains of a 
similar pyroxene. 

3. One of the most striking features of these remarkable rocks is the pseudo-porphyritic 
aspect due to the white or more rarely pink patches. Under the microscope these 
patches are seen to be in all cases aggregates. Orthoclase in the form of allotriomorphic 
grains is the principal constituent, but there is generally more or less of the substance or 
substances which gelatinise with hydrochloric acid and possess other characters indicating 
the former presence of nepheline and sodalite. Micro-pegmatitic intergrowths of felspar 
and the indefinite substance are not uncommon. We are indebted to Professor Derby 
of Sao Paulo for an interesting suggestion as to the nature of these patches. A 
specimen of the rock containing the white patches was given to him, and in writing to 

* Particulars as to the means by which wollastonite was identified are given because they do not appear to be 
generally employed by petrologists. It is often much easier to identify a mineral by studying the form and optical 
characters of the small fragments obtained by crushing than by examining thin sections. A description of the 
ordinary rock -forming minerals from this point of view would be of great service, and anyone who will undertake 
the work will confer a benefit on petrologists. . . 



176 MR J. HORNE AND MR J. J. H. TEALL ON BOROLANITE. 

one of us he sa3 T s : — " In preparing a specimen of your melanite rock, I cut through some 
of the white aggregates and was struck by the tendency to polyhedral outlines, which is 

not apparent on a broken surface but is quite distinct on the plane saw-cut face 

This to me is very suggestive of the pseudo-crystals of leucite in some of the related 
Brazilian rocks,* and suggests an interesting subject for investigation." In the same 
letter he says that he has found a micro-pegmatitic intergrowth of orthoclase and 
ncpheline in some of the pseudo-leucites. We have re-examined the whole of the material 
at our disposal, but are not able to add anything to what has been stated above. In 
addition to the constituents already mentioned as occurring in the white patches, we find 
also melanite, calcite and white mica. The melanite, however, is rare. It is always 
much less abundant in the patches than in the main mass of the rock. 

The matrix in which the white patches are embedded, and the entire rock-mass 
when these are absent, are composed of two or more of the constituents already enumerated. 
The type rock is essentially composed of orthoclase and melanite. A good idea of its 
microscopic character may be obtained from a glance at fig. 1, Plate XXXVII. 

As frequently happens when any extensive • mass of plutonic rock is examined there 
is considerable variation in the relative proportions of the different constituents, but this 
is not sufficient to take away from the orthoclase-melanite combination its dominant 
character. As illustrating the extremes of variation which have come under our notice, 
we may mention a rock from a point about one mile east of Aultnacallagach which is 
mainly composed of large individuals of orthoclase with a small quantity of the peculiar blue 
substance wedged in between the more or less idiomorphic crystals of the former mineral ; 
and one from the burn near Ledmore which consists of pyroxene, melanite, biotite, 
apatite and pyrite. One of these varieties consists, therefore, entirely of alumino-alkaline 
silicates ; the other almost entirely of ferro-magnesian minerals. The former occurs as a 
pegmatitic vein in typical borolanite. 

Another exceptional type was obtained on the north-west slopes of Cnoc-na-Sr5ine. 
It is essentially composed of orthoclase and pyroxene ; with biotite, sphene, apatite and the 
doubtful substance which gelatinises with hydrochloric acid as subordinate or accessory 
constituents. 

In the majority of cases the roeks are massive, but in some instances a well-marked 
foliation may be observed. In the foliated varieties the white patches have been 
orientated or even pulled out into lenticles and streaks. The movement probably took 
place during the final stages of consolidation. 

We have, then, a group of rocks especially characterised by the association of 
orthoclase and melanite. They are extensively developed in the neighbourhood of Loch 
Borolan, and as a new name appears to be required, we propose to call them borolanites. 
The typical rock is a crystalline granular aggregate of orthoclase and melanite. Biotite, 
pyroxene, alteration products after nepheline and sodalite, sphene and apatite, occur as 
subordinate and variable constituents. 

* See "On Nepheline Rocks in Brazil," Quart. Jour. Geol. Soc, vol. xlvii. (1891), p. 251. 



MR J. HORNE AND MR J. J. H. TEALL ON BOROLANITE. 177 

4. The affinities of borolanite are unmistakable. It is a member of the foyaite (elseolite- 
syenite) family. The occurrence of melanite as an important accessory in certain rocks 
belonging to the nepheline-leucite group has long been recognised. In our rock we have 
melanite raised to the rank of an essential constituent. Borolanite, as we have already 
shown, is intrusive in the Cambrian rocks of Sutherlandshire. The nearest rocks in any 
way allied to it are the elseolite- syenites of the Christiania district, which are also intrusive 
in Lower Palaeozoic strata. 

Appendix. 

So far as our own observations go, we have met with borolanite only in the neighbour- 
hood of the granitic mass of Cnoc-na-Sr5ine. Our colleague, Mr Hinxman, has observed 
a patch of borolanite intercalated in the thrust Eilean Dhu limestone at Elphin (Group 
II., Durness series, Cambrian). The rock is well exposed at the back of the Weaver's 
Cottage, south of the Elphin Schoolhouse ; it is in places highly decomposed, grey, with 
white knots and abundant melanite. Our colleague, Mr Gunn, has found dykes of the 
same type of rock in the area he has surveyed in West Ross-shire. He has kindly 
furnished us with the following note : — " In the Coigach district of West Ross-shire, about 
five miles to the north-west of Achiltibuie, there are found at Camas Eilean Ghlais two 
vertical dykes of borolanite intruded into the Torridon sandstone. They run in a general 
W.N.W. and E.S.E. direction, and vary considerably in width — the widest one east of 
the house being nearly thirty feet across, but further west only about six feet. This, 
which is the most southerly of the two, is also the longest, and can be traced for a length 
of half a mile or so/' 

A hand specimen of the rock is medium-grained, brownish-grey and massive. Lath- 
shaped cleavage faces of felspar may be seen with the naked eye. Numerous minute 
black specks (melanite), uniformly scattered through the rock, are visible with a pocket 
lens. 

Under the microscope the rock is seen to be composed of orthoclase, nepheline 
(partly fresh and partly altered to a substance giving aggregate polarisation), melanite, 
segirine and biotite. The main mass is an aggregate of orthoclase and nepheline or its 
alteration product. Traces of idiomorphism may occasionally be seen in both constituents, 
but, as a rule, the outlines of the individuals are not crystallographic faces. Melanite is 
scattered through the orthoclase-nepheline aggregate in small crystals of the usual form. 
In thin sections the crystals are either pale yellow or very deep brown. Not unfrequently 
a pale external zone surrounds a deeply coloured nucleus. 

iEgirine occurs in long prisms idiomorphic in the prismatic zone. The prisms are 
crowded together in certain portions of the slide, not uniformly scattered through it. This 
is the only rock in which we have detected typical segirine. In the other rocks the 
corresponding mineral is a green pyroxene with high extinction angles. The biotite 
occurs in the form of six-sided tablets. It is nearly opaque in thin sections when 



178 



MR J. HORNE AND MR J. J. H. TEALL ON BOROLANITE. 



viewed by rays vibrating at right angles to the principal axis, and appears a fiery 
reddish-brown when viewed by rays vibrating parallel with this axis. 

To remove all doubt as to the identification of nepheline, the following analyses were 
made : — 





I. 


II. 


III. 


Silica, ..... 


47-8 


47-9 


69-3 | 


Titanic acid, . 














•7 


n.e.* 




Sulphuric acid, 














•4 


n.e. 




Alumina, 
Ferric oxide, . 














20-1 
6-7 


21-8 | 
7-flt-J 


16-8 


Ferrous oxide, 














•8 


n.e. 




Manganic oxide, 














•5 


n.e. 




Baryta, . 














•8 


n.e. 




Lime, 














5-4 


5-1 


39 


Magnesia, 














1-1 


1-0 


•3 


Soda, 














5-5 


5-6 


4-6 


Potash, . 














7-1 


7-2 


1-7 


Loss on Ignition, 


• 










2-4 


2-4 


2-4 
















99-3 


98-6 


99-0 



I. Bulk analysis of the rock. For this analysis we are indebted to Mr J. 

Hort Player. 
II. Bulk analysis of another sample, by Teall. 

III. Analysis of the part soluble in hydrochloric acid from the same sample as No. II., 
by Teall. 

DESCRIPTION OF THE PLATE. 

Fig. 1. Typical borolanite from the north-west slope of Cnoc-na-Sr6ine. Magnified 33 diameters. Ordinary 

light. The minerals represented, are melanite, biotite (4) and orthoclase (6). The melanite is seen 

to be idiomorphic with respect to orthoclase and biotite. The felspar breaks up, under crossed nicols, 

into an aggregate of large irregular grains. 
Fig. 2. A rock essentially composed of orthoclase, pyroxene (3) and biotite, from the base of Cnoc-na-Sr6ine. 

Magnified 28 diameters. Ordinary light. This figure illustrates the general character of the pyroxene 

which occurs in the borolanite. The other minerals represented are orthoclase and magnetite (1). 

Under crossed nicols the individuals of felspar give more or less lath-shaped sections, and are in 

almost all cases twinned on the Carlsbad plan. 
Fia 3. Another portion of the same rock, also magnified 28 diameters. Sphene (2), pyroxene, biotite and 

felspar are represented. The sphene forms a large ophitic plate, all parts of which belong to one 

crystalline individual. 
Fig. 4. Portion of one of the white patches occurring in typical borolanite. One mile east of Aultnacallagach. 

This figure illustrates the peculiar micro-pegmatitic structure (8) referred to in the text. 
Fig. 5. The rock is similar to the one represented in figs. 2 and 3. It does not contain melanite. A portion 

of a large crystal of sphene is represented at the top of the figure. The other minerals are green 

pyroxene, felspar and pseudomorpha after idiomorphic nepheline (7) ? 



* Not estimated. 



t Total iron reckoned as ferric oxide. 



| Silica and insoluble residue. 



Trans. Roy. Soc. Eam r Vol. XXXVII. 



KEY PLATE 



Fl G. 2 



FIG. 3. 




MESS rs J.HORNE k J.J. H.TEALL ON BOROLANITE, 



M c Farlane &. Erskine. "Lith 1 "* Edin r 



Trans. Roy. Soc. Edm* Vol. AX AVI I. 

MESS rs J.HOKNE k J.J. H.'fEALL ON BOROLANITE. 




■11, del 



M'Farlane & Erskine. Lith'f Edin r 



( 179 ) 



XII. — On the Action of the Valves of the Mammalian Heart. By D. Noel Paton, 
M.D., F.R.C.P.E., Superintendent of the Research Laboratory of the Royal 
College of Physicians. (With Two Plates.) 

From the Research Laboratory of the Royal College of Physicians. 
(Read 4th January 1892.) 

Few subjects are of greater practical importance than the mode of action of the 
valves of the heart, inasmuch as these structures are so frequently the seat of patho- 
logical changes which produce serious disturbances throughout the whole circulatory 
system. 

On the general principles of the mode of action of the aortic and pulmonary valves 
all investigators seem to be agreed. When we turn to the auriculo-ventricular valves 
we find that, while in some of the best known text-books their action is considered as 
so thoroughly investigated and completely understood as to merit no discussion, and to 
require only the briefest description, in others the mechanism is admitted to be 
imperfectly comprehended, and is described in the most obscure and indefinite manner. 

In all, however, it is stated that the valves are raised at the commencement of 
ventricular systole to form a horizontal membranous septum between auricle and 
ventricle, and to prevent the regurgitation of blood from the latter cavity. 

Foster alone alludes to the possibility of the valves acting without being raised in 
this manner. 

This view was originated by Dr Richard Lower (Tractatus de Corde) in 1669. 
Its general acceptance seems to be due to the following causes : — 

First. The anatomy of the heart has almost universally been studied in the relaxed 
condition and by the ordinary methods of dissection. The sectional method has been 
employed only by one or two investigators, and in each case with a special purpose 
unconnected with the mode of action of the valves. 

Second. Various experiments on the dead heart have been accepted as illustrating 
the action of the valves in the living condition. Lower describes the now well-known 
experiment of cutting away the auricles and filling the ventricles with water through 
tubes placed in the aorta and pulmonary artery, and in this way causing the cusps of 
the auriculo-ventricular valves to be raised and applied to one another, so as to form a 
horizontal membranous partition between the auricles and ventricles — the chordae 
tendinese and papillary muscles playing a purely passive part in preventing the 
forcing of the valves into the auricles. 

An experiment which in so many important points fails to imitate the actual 
ventricular systole of the living heart cannot be deemed of much value. Yet probably 
no experiment has had so powerful an influence in establishing the present conception 

VOL. XXXVII. PART I. (NO. 12). • 2 E 



180 DR D. NOEL PATON ON THE 

of the action of the valves. The same objection applies to the more recent experiments 
of Sandborg and Worm-Muller. (Pfluger's Arch., Bd. 22, S. 108.) 

Third. The experimental observations of Chauveau and Faivre (Gaz. Med., 1856) 
on the heart of the horse during life have by many been accepted as strongly supporting 
this view. These investigators state that if the finger be introduced into the right 
auricle so as to palpate the valve, one feels at the moment of ventricular systole " les 
valvules triglochines se redresser, s'affronter par leurs bords, et se tendre au point de 
devenir convexes par en haut, de maniere a former un dome multiconcave audessus de 
la cavite ventriculaire." They made no experiments on the mitral valve. 

When, however, we come to examine this generally accepted view, several serious 
objections at once present themselves. 

First. The value of Chauveau and Faivre's observation is considerably diminished 
by the fact that subsequent observers have not confirmed it. 

Ktiss (Cours de Physiologie, 1872, p. 149) says, after giving the usual description 
of the closure of the valves, "Mais le fonctionnement est tout autre, car en introduisant 
le doigt vers le region auriculo-ventriculaire, au moment de la systole ventriculaire, on 
voit que l'espece d'entonnoir qui pend de l'oreillette dans le ventricule continue a 
exister." 

Second. It is impossible that the valves should be closed in the manner described. 
When the ventricle is fully distended, the chordae tendinese are stretched between the 
valves and the papillary muscles, as was clearly described in 1880 by Hesse (Arch. f. 
Anat. u. Phys., 1880, p. 346) ; and unless the first change in ventricular systole is a 
very marked shortening of the ventricular cavity, it would be impossible for the cusps of 
the valves to be raised into the horizontal position described, even if the papillary 
muscles did not, from the first, participate in the contraction of the walls of the chamber. 
Now Hesse has clearly shown that even in the third stage of ventricular systole the 
apices of the papillary muscles are only very slightly approximated to the auriculo- 
ventricular orifice. 

Third. If the valves are closed as usually described, a large part of the mass of blood 
which is lying between the cusps must be forced back into the auricles, and thus a 
considerable regurgitation must occur. 

Fourth. The horizontal septum between auricle and ventricle formed by the elevated 
valves is composed of a comparatively thin membrane. When the auricle relaxes, as 
ventricular contraction goes on, this membrane must be subjected to a sudden and 
enormous pressure, amounting in the left ventricle to about 3450 grms., and in the 
right to 1664 grms. (Onimus, Journal de VAnatomie, 1865, p. 351), which its structure 
is not specially adapted to withstand, and which certainly one must, a priori, anticipate 
would tell prejudicially upon such living membranes. In short, the mechanism as usually 
described is a bad one. 

Fifth. It appears strange that such well-developed structures as the papillary muscles 
should play so small a part in the action of the structures into which they are inserted. 



ACTION OF THE VALVES OF THE MAMMALIAN HEART. 181 

Finally, if the valves act as described in Landois and Stirling (3rd ed., p. 59) and 
many other text-books, the ventricles can never be even approximately completely 
emptied. A large supra-papillary space must always remain filled with blood. 

These considerations have led me to reinvestigate the question of how the auriculo- 
ventricular valves are closed, and how they prevent the regurgitation of blood into the 
auricles. 

It is at once obvious that these valves might fulfil their function of preventing 
regurgitation in just as perfect a manner and without the severe strain, which, according 
to the presently accepted theory, they have to bear with each systole, if, instead of being 
raised to form a horizontal septum, their cusps were simply applied face to face to one 
another. In this way all passage of blood between the cusps would be prevented, 
while at the same time the segments would afford one another mutual support. 



Method. 

My object was, if possible, to fix the heart in the various stages of the cardiac cycle, 
to harden it, and by sections and dissection to determine the position of the valves in 
the various phases, so that an actual demonstration of the true condition might be 
afforded. 

Eabbits were chiefly used, on account of their being of convenient size and easy to 
procure, but many observations were also made upon the hearts of cats, dogs, sheep, and 
men. 

The Rabbit was killed by a blow behind the head. The thorax was then rapidly 
opened, the larger vessels being carefully avoided to prevent loss of blood, and the peri- 
cardium was slit up. The method of procedure then varied according to the condition 
in which it was desired to fix the heart. To imitate the third stage of ventricular systole* 
during which the ventricle remains contracted after the expulsion of the blood, clamps 
were applied on the large vessels and the organ was excised and plunged momentarily 
into boiling water, the clamps being taken off at once. This procedure produced a gush 
of blood from the great arteries and a smaller flow from the great veins, and fixed both 
auricles and ventricles in a firmly contracted condition. 

To imitate the first stage of ventricular systole — the contraction of the ventricles 
before blood is expelled into the arteries — is more difficult ; because when respiration 
stops the right heart becomes engorged with blood. 

The method of procedure was to expose the heart as above described, and then to 
ligature or clamp the great vessels, and to plunge the ventricles for a second or two into 
boiling water or hot perchloride of mercury solution, care being taken to prevent such 
overheating as would distort the valves and chordae. This at once caused a contraction 
of the ventricles ; . but this was frequently accompanied by a regurgitation into the 



182 DR D. NOEL PATON ON THE 

auricles. This was probably due to the fact that the papillary muscles were not 
directly stimulated, and that therefore the closure of the valves was not complete. Indeed, 
on account of the indirect stimulation of the papillary muscles as compared with the 
ventricular wall, this method would specially favour the assumption of a horizontal posi- 
tion of the cusps of the valves. 

To fix the heart in diastole the vessels were ligatured, arid the organ was suspended 
in water until rigor-mortis had passed off, and was then hardened first in Muller's solution 
and then in alcohol. 

With dogs and cats the animal was killed with chloroform, and the heart rapidly 
excised and treated as above described. 

For the human hearts I have examined, I have to thank Dr Barrett, who was good 
enough to let me have a number of unopened hearts from the post-mortem room of the 
Royal Infirmary. Most of these were lax, post-mortem rigidity having passed off". By 
removing the clots, filling the cavities with spirit and hardening, one was able by making 
sections to study the relationship of parts in diastole. Some specimens were obtained in 
the condition of rigor-mortis, and these, after hardening in spirit, showed to some extent 
the relationship of parts in the third stage of ventricular systole. But inasmuch as 
the factor of blood-pressure had not had full play, the valves were never found in quite 
the same position as in the heart prepared as described above. 

I am also indebted to Dr Gibson for a number of specimens of hearts from young 
subjects, which had been hardened in the condition of more or less firm rigor-mortis, and 
from which some of the figures were prepared. 

Sections were made in different planes, but chiefly in those indicated in fig. 4. The 
sections were photographed, either before or after removal of the coagulated blood, and 
then preserved in spirit. 

In this way a very complete picture was obtained of the position of the valves during 
the various phases of the cardiac cycle, while the mechanism by which the various 
changes are produced was also rendered clear. 



Anatomical Considerations. 

It will be necessary, in the first place, merely to allude to certain points in regard to 
the position of the orifices, valves, papillary muscles, and chordae tendinese. Although 
these matters are dealt with in anatomical works, the descriptions given are far from 
complete or satisfactory. 

The chordae tendinese are not, as is usually described, entirely inserted into the margins 
and ventricular surfaces of the valves, but are to a large extent continued upwards along 
the surface of the valves, to be inserted into the auriculo-ventricular rings (fig. 6). Dr 
Symington has shown me a specimen in which the muscular fibres of the papillary muscle 
are continued upwards and inserted into the auriculo-ventricular ring. When the papil- 



ACTION OF THE VALVES OF THE MAMMALIAN HEART. 183 

lary muscles contract, they will therefore tend to pull the rings downwards and inwards 
and thus to diminish the auriculo-ventricular opening and the ventricular cavity, and to 
assist in the expulsion of the blood. 

The left ventricle forms a central cylindrical core to the heart ; and to one side of 
this the right ventricle is attached along the anterior and posterior sulci (figs. 1, 2, 3). 

The right ventricle is formed of an outer and an inner wall — the latter, the so-called 
septum, being really part of the wall of the left ventricle, and bulging into the cavity 
of the right ventricle as a surface that is convex, not only from before backwards, but 
also from above downwards (figs. 1, 2, 3, 7, 10). 

It is triangular in shape. At the anterior and upper angle is the orifice of the pul- 
monary artery. The inferior angle is at the apex. The anterior and posterior sides of 
the triangle correspond to the anterior and posterior sulci. The superior side is com- 
posed in front of the pulmonary orifice ; behind this, of the upper and right wall of 
the conus arteriosus ; and still further back, at the posterior and upper angle is the 
auriculo-ventricular orifice (fig. 3). 

This opening, in the normal position of the heart of Man, faces to the left forwards 
and downwards. It is surrounded by muscular fibres. In diastole it is elliptical, but in 
the fully contracted condition it is reduced to little more than a slit. 

The distribution of the papillary muscles varies in different animals ; but in all, an 
anterior group of small muscular processes is present, situated just behind and below the 
pulmonary orifice, having a somewhat horizontal direction, and connected by chordae 
tendineae with the anterior borders of the infundibular and septal cusps of the tricuspid 
valve (figs. 3, 6). The arrangement of the anterior and posterior sets of papillary 
muscles varies considerably. In the Eabbit (fig. 4), where there is only a small amount 
of trabecular tissue towards the apex of the ventricle, these muscles arise from the 
septum. In Man (fig. 6), where the lower or apical third of the ventricle is composed of 
a network of muscular trabeculae, the papillary muscles take origin most usually from 
fibres of that network running between the septum and the outer wall — sometimes in 
close relationship to the septum, sometimes more intimately connected with the external 
wall. In the latter case the governor band is well developed. 

They may be described as four in number — if we include the anterior muscle situated 
under the pulmonary artery (fig. 6). 

1st. Superior, situated just under the pulmonary orifice, directed backwards and to 
the right, and sending chordae to the anterior margins of the septal and infundibular 
cusps of the tricuspid. These chordae have a transverse direction. 

2nd. Anterior takes origin from the trabecular tissue at the apex towards its anterior 
part, and is directed upwards. It gives off chordae to the posterior margin of the 
infundibular cusp, and to the anterior margin of the posterior cusp. 

3rd. Posterior takes origin from the trabecular tissue near the apex posteriorly, 
is directed upwards, and gives off chordae to the posterior margins of the posterior and 
septal cusps of the tricuspid. 



184 DR D. NOEL PATON ON THE 

4Jh. A number of small prominences arising from the septum give chordae to the 
inferior margin of the septal cusp, and bind it down to the septum. 

Contraction of the superior and anterior of these muscles, through their direction and 
from the curvature of the septum, will stretch the infundibular cusp against that wall of 
the ventricle. At the same time the various papillary muscles will pull the different 
cusps together, while the posterior papillary muscle will pull the posterior cusps against 
the curved septum. 

5th. Left Ventricle. — The left auriculo- ventricular orifice is situated posteriorly, 
facing downwards, forwards, and to the left (in the normal position of the heart in Man). 
In diastole, it is nearly circular (fig. 5). In systole, it is reduced to a transverse slit. 
In front and to the right of this is the aortic orifice, separated from it only by a mem- 
branous wall. 

The anatomical position and characters of the two cusps of the mitral valve, and the 
separation of the papillary muscles into two sets, an anterior or left (figs. 1 and 2), the 
chordse of which are connected with the left edges of the anterior and posterior cusps, 
and a posterior or right (figs. 1 and 2), with cords attached to the right edges of the 
cusps, are so well known as merely to require mention. The chordse connected with the 
posterior cusp are largely inserted into the auriculo-ventricular ring. 



Action of the Valves. 
Position of Valves in Ventricular Diastole. 

When an attempt is made to study this question in the usual way by dissection of 
the heart, the results are rendered fallacious by the fact that rigor-mortis is frequently 
present, or that the organ is so limp that the relations of the various parts are not 
preserved. 

It may be best investigated in hearts prepared as described on p. 182. 

In order to demonstrate the position of the parts of the tricuspid valve, sections are 
best prepared in a vertical transverse plane (fig. 5, A). For the mitral valve, on the 
other hand, the sections should run in a plane (fig. 5, B), passing through the orifice of 
the aorta and the left auriculo-ventricular orifice. 

Tricuspid Valve. — The septal cusp is applied to the wall of the septum (fig. 7). 
The two outer cusps extend downwards and somewhat inwards, so that a flattened 
funnel-shaped orifice, narrow in front and broad behind, between auricle and ventricle is 
formed (figs. 3 and 7). 

Mitral Valve. — The posterior cusp lies against the posterior wall of the ventricle. 
The anterior cusp extends downwards, and somewhat to the left (figs. 8 and 9). 



ACTION OF THE VALVES OF THE MAMMALIAN HEART. 185 

Position of Valves in Ventricular Systole. 

In studying the position of the valves during this period, its division into three 
phases, more or less distinctly marked, must be remembered. 

1st. Latent Period, — before the opening of the aortic and pulmonary valves, during 
which the pressure in the ventricle is being got up. 

2nd. Expulsion Period —-during which the great mass of blood is being expelled 
through the arterial orifices. 

3rd. Period of Residual Contraction, — during which the ventricles remain con- 
tracted, and may expel any blood not driven out during the last period. According to 
HtJRTHLE this period is simply the terminal stage of the second period. 

1st — Latent Period. 

Right Ventricle. 

The heart having been fixed as described on p. 181, the following condition of the 
various parts was observed : — 

a. Tricuspid Valve. — On making sections, the septal cusp is found more or less 
closely applied to the septum, while the two external cusps are pulled towards the septum 
(fig. 10), and the infundibular cusp is pressed closely against it from the action of the 
superior and anterior sets of papillary muscles. At the same time the outer part of the 
auriculo-ventricular ring is pulled downwards and inwards, by the combined action of 
the papillary muscles and chordas inserted into the ring and the muscular fibres 
surrounding the orifice. 

b. Ventricular Cavity. — The external wall of the ventricle is pulled nearer to the 
septum ; and the anterior wall, under and in the region of the conus, bulges forward. 
This is due to the greater thickness and power of the muscular fibres at the apex and 
right side of the ventricle, and to the comparative thinness of the wall in the region of 
the conus. This I believe to be a matter of some importance in explaining the increase 
in the antero-posterior diameter of the heart, and the diminution in the transverse 
diameter described by various investigators. 

The change in the antero-posterior and transverse diameters of the heart may be shown 
not only by tracings taken from the living organ, but can also be demonstrated by fixing 
the heart in the various phases of the cardiac cycle. 

This has already been done by Ludwig and Hesse (Arch, f Anat. u. Phys., Bd. 18), 
but their observations refer merely to the state of diastole and to the third stage of systole 
when the ventricles have already expelled their contents. 

By adopting the method already described I have been able to fix the heart in the 
first stage of ventricular systole, and by careful measurement to show that a distinct 
increase in the antero-posterior and a diminution in the transverse diameter of the organ 
occurs. This is clearly shown in the accompanying tables and set of figures. 



186 



DR D. NOEL PATON ON THE 



Exp. I. 



Heart of Cat. 



Distance from 
Apex in mm. 



25 



Heart of Cat. 





Distance from 
Apex in mm. 



20 



Diastole. 


Systole. 


Distance 

from Apex 

in mm. 


Transverse 

Diameter 

in mm. 


Antero- 
posterior 
Diameter 
in mm. 


Transverse 
Diameter. 
Antero- 
posterior 
Diameter. 


Distance 

from Apex 

in mm. 


Transverse 

Diameter 

in mm. 


Antero- 
posterior 
Diameter 

in mm. 


Transverse 
Diameter. 


Antero- 
posterior 
Diameter. 


10 
17 
25 


25 
30 
30 


18 
21 

25 


1-4 

1-4 
1-2 


12 

18 
20 


24 

27 

27 


20 
28 
27 


1-2 
0-9 
1-0 



T. D. = 30 mm. 
A. P. D. = 25 mm. 



27 mm. 
27 mm. 



17 




T. D. = 30 mm. 
A. P. D. = 21 mm. 




27 mm. 
23 mm. 



18 



10 




T. D. = 25 mm. 

A. P. D. = 18 mm. 

Diastole. 




24 mm. 
20 mm. 

Systole. 
(First Stage.) 



12 



Exp. II. 



Heart op Cat. 



Greatest Diameter. 


Diastole. 


Systole. 


Longitudinal, ...... 

Antero-posterior, ...... 

Transverse, ....... 

Transverse 

Antero-posterior, ..... 


33'1 mm. 

20-4 mm. 
26 - 4 mm. 

1-3 


33*1 mm. 
2 5 '5 mm. 
25*5 mm. 

1-0 



ACTION OF THE VALVES OF THE MAMMALIAN HEART. 187 

In the human heart the drawing towards the septum of the external wall of the 
ventricle is favoured by the muscular trabecule in the lower part of the ventricle. The 
auriculo-ventricular ring is drawn downwards and inwards by the chordae tendineas 
passing to it, while the infundibular cusp of the tricuspid from the lines of traction of its 
chordae tendineae must be flattened against the bulging septum. Its posterior margin is 
approximated to the anterior edge of the posterior cusp, which with its posterior edge in 
contact with the posterior margin of the septal cusp is pulled downwards into the 
posterior angle of the ventricle against the curve of the septum. 

Left Ventricle. 

The Cavity of the Ventricle becomes narrower from side to side, and wider from before 
backwards. At the same time the posterior cusp of the Mitral Valves is raised from the 
ventricular wall and pulled forward by the chordae tendineae towards the anterior cusp, 
which is at the same time pulled backwards so that the two are applied face to face (fig. 11). 

And now, one function of the papillary muscles and anterior cusp of the valve becomes 
very apparent. By their action on the membranous part of the auriculo-ventricular ring 
forming the posterior wall of the aorta, from which the cusp takes origin, they help to 
keep open the aortic orifice, which would tend to be pressed upon and closed by the con- 
traction of the muscular fibres extending;; round the aortic and mitral orifices. The 
direction obliquely backwards taken by the membrane between the aorta and the 
auriculo-ventricular orifice is well seen in figs. 8 and 11. 

Onimus partly appreciated this action of the large segment of the mitral valve 
{Journal de V Anatomie, t. 2, p. 376). 

2nd — Period of Expulsion. 

It is, of course, impossible to fix the ventricle in this phase. But from a study 
of the first and third period we can form a clear picture of what occurs during this 
period. On the right side, the blood collected in front and to the right of the tricuspid 
valve and accumulated in the conus is shot into the pulmonary artery, the outer wall 
approaching the septum and the auriculo-ventricular orifice being narrowed. 

On the left side, the posterior-ventricular wall contracts on the posterior cusp of the 
mitral, forcing the blood round the valve, to be expelled along with the mass of blood 
accumulated in front of the anterior cusp. 

3rd — Period of Eesidual Contraction. 
Right Ventricle. 

The auriculo-ventricular opening is reduced to crescentic slit. The cavity of the 
ventricle is flattened from side to side and obliterated ; except just under the pulmonary 
artery, where a small cavity, resembling a flattened and inverted cone, is left filled with 

VOL. XXXVII. PART I. (NO. 12). 2 F 



188 DR D. NOEL PATON ON THE 

blood. The septal cusp of the valve is applied flat against the septum ; the infundibular 
and posterior lie flat against it, — only a small wedge-shaped mass of blood continuous 
with the auricular contents lying between the valves at their upper part (fig. 12). 

Occasionally extremely instructive casts of the inter-valvular space may be seen in 
post-mortem examination of the human heart in which a blood clot has formed. This clot 
shows a thin flattened anterior part where the anterior cusp has been pulled against the 
septum, and a thicker, more conical posterior portion. Such a cast is figured by 
Pettigkew (Proc. of the Royal Soc, vol. xxiii. part iii., 1864). 

Left Ventricle. 

The auriculo- ventricular orifice is reduced to a transverse slit. The cavity of the 
ventricle is entirely obliterated, except for a cylindrical part filled with blood im- 
mediately under the aortic orifice. The posterior cusp of the mitral is applied against 
the posterior wall of the ventricle ; and the anterior lies in front of it, and applied to it 
throughout the lower part of its extent. A wedge of blood from the auricles extends 
down between the upper part of the valves. No strain is put on the membranes, which 
mutually support one another (fig. 13). 

Such a series of observations seem to demonstrate beyond a doubt that the mechanism 
of the auriculo-ventricular valves is very different from that so universally described. 

Instead of the cusps of the valves being floated into a horizontal position to form a 
septum between auricles and ventricles, they are simply applied face to face, and thus 
prevent all regurgitation without being subjected to any strain. At the same time, 
their depressed position gives the ventricles a core upon which they can contract to 
completely empty themselves into the arteries. 

It may be objected to this view that it does not account for the valves being closed 
before the ventricular systole begins, so as to prevent regurgitation at the commencement 
of the systole. But such a closure, before ventricular systole, is not necessary, for it has 
been shown that the auricles do not relax until after the commencement of ventricular 
systole, and of course, until these chambers pass into diastole, no reflux flow is possible. 
Hence a closure at the commencement of the systole is all that is required. 

It may perhaps also be urged that, although in these preparations the valves are 
found closed as above described, they may have become occluded in the manner usually 
described, and subsequently pulled downwards, as described by Kuhschner (Wagner's 
Handwbrterbuch, Bd. ii. S. 60, 1844), Lcjdwig ' (Lehrbuch du Physiologic, Bd. ii. S. 61, 
1856), and Pettigeew (Trans, of the Royal Soc. of Edin., vol. 23, part iii., 1864). A 
moment's consideration will show that this is impossible. For, once closed in the hori- 
zontal position, it would be impossible to have them pulled downwards until blood had 
left the ventricles, since the fluid blood is incompressible. 

Again, the recent researches of Roy and Adami (Practitioner, 1890) on the action of 
the papillary muscles, independently of and later than the general heart muscle, might 



ACTION OF THE VALYES OF THE MAMMALIAN HEART. 



189 



indicate an objection to this theory. Unless the papillary muscles act almost synchro- 
nously with the rest of the muscle substance, it is not easy to conceive that the valves 
could be closed in the manner described. 

While fully recognising the value of their work, I do not think that they have con- 
clusively proved their contention that the contraction of the papillary muscles is later 
than that of the ventricular wall. 

The papillary muscles are nothing more or less than special developments of the 
trabecular tissue of the foetal heart from which the columnse carnese also spring. They 
are, in fact, simply columnse carnese ; and all gradations may be traced from the large 
papillary muscles through the small muscular 
prominences giving origin to a single cord, to 
the proper muscular substance of the heart. 
In the left ventricle of the rat the two papillary 
muscles are replaced by two columnse carnese, 
from the sides of which the chordae tendinese 
spring. Which of these papillary muscles 
contracts after the heart substance, and which 
contract with it ? It would indeed be curious 
to find a delay in the contraction of certain of 
these muscles and not in others. 

But a careful study of their work by no 
means bears out their conclusions as to the 
late contraction of these muscles. Undoubtedly 
these structures shorten greatly and still further 

pull down the valves at a period later than the commencement of the contraction of the 
ventricles, just at the time when the blood is expelled into the arteries. Roy and Ad ami 
look upon this as the cause of the expulsion of blood ; but it is much more probably the 
result. Until the semilunar valves are opened, and the blood begins to leave the ven- 
tricles, the papillary muscles may enter into a state of contraction ; they may approxi- 
mate the cusps of the valves, but they cannot pull these down upon the ventricular con- 
tents. As the blood, however, passes out, these structures can shorten ; and their 
shortening may influence the long and transverse diameter of the ventricles, as described 
by these authors. 

Farther, as a result of their researches, Fenwick and Overend (Brit. Med. Journal, 
vol. i. p. 1118, 1891) conclude that it is "extremely probable that the shortening of the 
two muscles (i.e., the wall muscles and papillary muscles) under normal circumstances is 
practically simultaneous." 

A review of the older work upon this subject — which undoubtedly points to the 
simultaneous action of papillary muscles and ventricular wall — will be found in a paper 
by See (see p. 191). 

So far as our evidence at present goes, we must conclude that the papillary muscles 




190 



DR D. NOEL PATON ON THE 



contract along with the rest of the ventricular wall, and close the valves as above 
described. 

It may be asked, " If this is the mode of action of the tricuspid valve, what is the 
meaning of the small internal cusp ? " Possibly, with a small amount of blood behind it, 
it may act as a cushion against which the external cusps may rest. It is, however, more 
probably simply to be regarded as a developmental remnant of the " Ohrkanal " described 
by His, from the walls of which the auriculo- ventricular valves are developed. 

Many of the older physiologists have fully appreciated the difficulties in the acceptance 
of the commonly taught theory, and, from a consideration of the anatomy of the heart, 
have been led to advocate the view, the correctness of which, I believe, I have succeeded 
in demonstrating. 

Meckel (Handbuch der menschlichen Anatomie, Bd. iii. S. 23, 1817) appears to 
have been the first to suggest that the valves were closed as above described. 

After describing the papillary muscles, he says,' — " Indem diese sich bei den 
Zusammenziehungen des Herzens verktirzen, werden die verschiednen Abschnitte der 
Klaj)pen in die Hohle des Herzens einander gegen gezogen, und so die Mundung 
kraftig geschlossen. " 

Mayo, in 1829, gave a very clear description of the action of the valves. The 
following is taken from his Outlines of Physiology, 4th edition, 1837, p. 42. 

" The action of these fleshy columns, and of the tendinous cords in closing the valve, 
may be easily understood from the adjoining figures. 

" Fig. 1 represents the mitral valve during the diastole of the ventricle, the fleshy 

columns relaxed, the chorda? tendinese loose, the passage 
through the auricular valve patulous. 

" Fig. 2 represents the condition of the valve during the 
ventricular systole : its edges are then drawn into contact, so 
as to form a kind of flattened conical projection into the 
ventricle." 

He considers that the action of the tricuspid valve takes 
place on the same principle as that of the mitral, and that it 
is never properly closed. 

Eeid, in his article on the heart in Todd's Cyclopedia of 
Anatomy and Physiology, 1836, says, "That the lips of the 
valves are approximated in this manner " (described by Mayo) " appears to me to be the 
much more probable opinion." 

Hope (Diseases of the Heart, 1839) gives a very similar description of the action of 
the valves, and states that the credit of originating the theory belongs to Mayo. 

Burdach (Traite de Physiologic, traduit de VAllcmand sur la deuxieme edition, par 
A. J. L. Jourdon, 1827, t. vi. p. 239) develops precisely the same theory. 

In an admirable treatise, " Du Cceur, de sa structure et de ses mouvements, ou Traite 




ACTION OF THE VALVES OF THE MAMMALIAN HEART. 



191 



anatomique, physiologique et pathologique des mouvements du coeur de l'homme," pub- 
lished in 1848, M. Parchappe, Professeur de Physiologie a l'ficole de Medecine et de 
Pharmacie de Rouen, after describing most fully the structure of the various cavities and 
valves of the heart, describes the auriculo-ventricular valves as closing the orifices by 
being applied face to face. 

M. Berard, in his Cours de Physiologie, puts this theory of Parchappe's even 
more clearly. 

Professor Ktiss of Strasbourg (Manual of Physiology, being a course of Lectures 
delivered by Professor Kilss at the Medical School of the University of Strasbourg, edited 
by M. Duval, and translated by Robert Amory, M.D., 1875, pp. 134, et seq.) elaborates 
this theory at great length. 

He considers that the auriculo-ventricular valves, with the space between them, are 

" only movable continuations of the auricle acted on by certain muscular powers 

The first result of the contraction of the papillary muscles is the lengthening of the 
auricular cone, the edges of which are afterwards brought near each other. While this 
hollow cone descends into the ventricles, the sides of the latter contract, and approach 
the cone in such a manner that the auriculo-ventricular apparatus acts as a sort of hollow 
piston, which penetrates the ventricle and comes into close contact with its wall ; and 
thus the ventricle empties itself completely, the 
contact becoming perfect between its sides and the 
auricular prolongation." 

As already mentioned, he distinctly states that 
by the finger inserted into the auriculo-ventricular 
opening, we can detect that the space is not oc- 
cluded as described by Chaxjveau and Faivre. 

To a certain extent he is right ; but it is impos- 
sible that the small auricular pressure could main- 
tain the valves in the condition shown in his figure, 

convex towards the ventricular cavity, against the enormously greater ventricular 
pressure. What really occurs is, that the valves are pressed face to face throughout 
the greater part of their extent ; and that only between their upper parts is auricular 
blood to be found — the space for it being maintained by the tension of the valves. In 
the mitral valve, when the large anterior cusp forms what Onimus described as the 
central septum of the ventricular cavity, this space is specially well marked. 

In a long and exhaustive paper (Archives de Physiologie, 2nd series, t. i., 1874, pp. 
552 and 848), M. Marc See, after giving a very full historical account of the work already 
accomplished on the subject, from a careful consideration of this work and of the anato- 
matical relationship of the valves, comes to the following conclusions in regard to their 
mode of action : — 

"3°. Les muscles papillaires des valvules se contractent en meme temps que l'ensemble 
des parois ventriculaires. 





Fi«. 38.— Showing the 
auriculo - ventricular 
system during the re- 
pose of the ventricle. 



Fig. 39.— Showing the auri- 
culo-ventricular apparatus 
during the contraction of 
the ventricle. 



192 DR D. NOEL PATON ON THE 

" 4°. La contraction des muscles papillaires a pour effet la tension des cordages 
tendineux et l'abaissement des valvules. Cet effet se produit malgre le raccourcissement 
systolique du diametre longitudinal des ventricules, admis par la plupart des auteurs. 

" 5°. Les muscles papillaires du ventricule gauche sont disposes de facon a. s'emboiter 
l'nn dans l'autre et a combler la portion gauche de la cavitd ventriculaire. En se 
contractant, ils attirent a gauche les deux valves de la mitrale, qu'ils appliquent Tune sur 
L'autre et contre la paroi du ventricule. La valve droite joue le role essentiel dans 
l'occlusion de l'orifice auriculo-ventriculaire ; mais la valve gauche n'est pas inutile, non 
plus que les deux languettes valvulaires accessoires. 

" 6°. Le mode de resserrement du ventricule droit differe notablement de celui du 
ventricule gauche, ce qui a necessite des dispositions particulieres dans la valvule 
tricuspide. 

"7°. Les muscles papillaires du ventricule droit, en se contractant, appliquent et etalent 
les valves de la tricuspide a, la surface de la cloison. La forme convexe de cette derniere 
rend compte de l'existence de trois valves dans le cceur droit. 

"8°. II y a dans la paroi ventriculaire droite un gros faisceau musculaire dont Taction 
supplee celle de la pression sanguine, si considerable dans le ventricule gauche. Ce 
faisceau musculaire est l'analogue du demi-sphincter qui remplace la valvule tricuspide 
dans le cceur des oiseaux." 

These conclusions have been arrived at by reasoning from the anatomy of the heart 
as demonstrated in the ordinary methods of dissection, aud from experiments on the dead 
and flaccid heart, but not from any direct observations. 

The adoption of this view as to the mode of action of the auriculo- ventricular valves 
will modify our conception of the mechanism of regurgitation. 

It has always been difficult to understand how, with even a small degree of dilatation 
in cardiac debility, regurgitant murmurs are produced. 

The valves are so large in relationship to the orifices (Hermann's Handbuch der 
PJiysiologie, Bd. vi. S. 161) that one should expect that even though the dilatation 
were very considerable, if the valves assumed the horizontal position usually described, 
the occlusion would be complete. 

When, however, we consider the importance of the action of the papillary muscles 
in the closure of the valves, and when we remember that their vascular supply is a 
terminal one, and that they are therefore early the seat of degenerative changes (Fenwick 
and Overend, loc. cit.), and when we recall the fact that in abnormal conditions of the 
heart these muscles do not act so promptly as they should do, we can readily see that 
the valves will frequently not be closed before auricular dilatation commences, and that 
thus a back flow of blood will occur. This will be specially apt to happen on the right 
side of the heart. 

Again, to close the orifices in the manner we have described requires valves of con- 
siderably greater size than would be necessary to occlude the orifice in the horizontal 



ACTION OF THE VALYES OP THE MAMMALIAN HEART. 193 

position. Hence, when even a slight engorgement of one side of the heart occurs, we may 
have an incomplete occlusion and regurgitation. This state of things is well seen in 
the heart of a rabbit which is much engorged. Marked regurgitation into the right 
auricle occurred when the ventricles were dipped in the boiling solution. In all my 
experiments with engorged hearts, this regurgitation occurred very much more readily 
on the right side. The safety-valve action of the tricuspid is to be explained in this 
way. 

Again, it is often difficult to explain on the usual theory of occlusion how organic 
lesions so modify the action of the auriculo- ventricular valves as to allow of regurgita- 
tion. In these cases, if water be injected from the aorta, the mitral is floated up and 
seems to act satisfactorily. And yet during life, regurgitation occurred. A roughening 
or crumpling which would not be sufficient to prevent the adaptation of the segments 
to one another in the horizontal position, might be sufficient to prevent their close 
adaptation, face to face, and might thus allow of a back flow through the valve. 



Aortic and Pulmonary Valves. 

Support of Valves. 

In connection with these valves, an extremely interesting mechanism is to be observed, 
whereby the cusps are protected from and supported against the great strain of the 
arterial pressure. 

Aortic Valve. — An examination of antero-posterior sections (figs. 8 and 9), and 
of preparations of the base of the heart (fig. 4), shows that the anterior cusp of the 
aortic valve is placed upon the top of a muscular cushion formed by the upper part 
of the septum ventriculi. Upon this cushion the blood filling the Sinus of Valsalva 
will rest. Now Pettigrew (Transactions of the Royal Society, 1864) has shown by a 
series of casts in plaster of Paris that this cusp closes before the other two, which, to use 
his expression, are twisted down upon it. Thus the muscular cushion supporting 
the pressure in the anterior sinus will also support the pressure in the sinuses of 
the two posterior cusps, and will thus diminish the strain put upon the cusp of the 
valve. 

Pulmonary Valve. — Though not so well marked, a similar cushion arrangement is to 
be found in connection with the pulmonary valve when the postero-sinistral cusp of the 
valve is set upon the upper part of the septum ventriculi, which forms a cushion 
underneath it. The two other cusps are at a somewhat higher level and will rest upon 
the first, thus participating in the support of the septum. 

I was for long unable to find any reference to this mechanism, but Sir William 
Turner referred me to a paper by Savory, Lancet, vol. ii., 1854, in which this 
muscular cushion is clearly described and figured. 



194 ACTION OF THE VALVES OF THE MAMMALIAN HEART. 

Prevention of Occlusion of Aortic Orifice. 

The manner in which the anterior cusp of the mitral valve, from its obliquity and 
connection with the membranous septum between the aorta and the auriculo-ventricular 
opening on the one hand, and the papillary muscles on the other, assists in preventing 
the occlusion of the aortic orifice, has been described on p. 187. 



EXPLANATION OF PLATES. 

Plate I. 

Fig. 1. Transverse section through middle third of ventricles of human heart (rigor-mortis) to show relation- 
ship of cavities, and bulging of septum into right ventricle, b, anterior papillary muscle of right 
ventricle ; c, posterior papillary muscle of right ventricle ; d, anterior papillary muscle of left 
ventricle ; e, posterior papillary muscle of left ventricle. Natural size. 

Fig. 2. Transverse section through lower third of ventricles of human heart (relaxed) to show trabecular 
structure at apex of right ventricle, with origin of papillary muscles, b anterior, and c posterior; 
a anterior, and e posterior, papillary muscles of left ventricle. \\ natural size. 

Fig. 3. Transverse section through upper third of ventricles of human heart (relaxed), looking upwards, to 
show relationship of pulmonary orifice, conus, and right auriculo-ventricular orifice with tricuspid 
valve, a superior, b anterior, and c posterior papillary muscles; d infundibular, e posterior, 
and / internal cusps of valve. Note greater thickness of ventricular wall laterally than in front. 
On left side mitral valve x situated behind and to the left. 1^ natural size. 

Fig. 4. Right ventricle of rabbit's heart to show papillary muscles taking origin from septum. Natural size. 

Fig. 5. View of ventricles from above (heart of child), auricles removed. Shows planes of section to de- 
monstrate mitral (B) and tricuspid (A) valves. Natural size. 

Fig. 6. Right ventricle of heart of adult man, to show stretching of infundibular cusp of valve, between 
superior and anterior papillary muscles. Letters as in 3. About \ natural size. 

Plate II. 

Fig. 7. Vertical transverse section of adult human heart in diastole (looking backwards), to show position 
of tricuspid valve, t, trabecular structure at apex of ventricle from which papillary muscles 
rise ; b, anterior muscle ; d, infundibular cusp of valve ; h, internal cusp ; v, posterior wall of 
left ventricle. \ natural size. 

Fig. 8. Vertical antero-posterior section of left ventricle of adult human heart in diastole (in line B, fig. 
4), looking to left, b, anterior cusp of mitral valve ; a, posterior cusp somewhat displaced from 
its position against the posterior wall of the ventricle ; d, anterior papillary muscle ; au, left 
auricle; as, aorta; rv, conus of right ventricle; c, muscular cushion under right anterior cusp 
of aortic valve \ natural size. 

Fig. 9. Vertical antero-posterior section of heart of sheep (somewhat more antero-posterior than 8). Heart 
in semi-rigor — letters as in 8. I, posterior papillary muscle, \ natural size. 

Fig. 10. Vertical transverse section of heart of rabbit fixed in the first stsge of ventricular systole, to show 
mode of closure of tricuspid valve. /, internal cusp applied to septum ; d, external cusp drawn 
in upon septum ; p, papillary muscle. (From a drawing.) Natural size. 

Fig. 11. Vertical antero-posterior section of heart of rabbit in first stage of ventricular systole, blood removed 
from left ventricle. Shows application of anterior and posterior cusps of mitral valve to occlude 
auriculo-ventricular orifice, ao, aorta; au, left auricle; ac, anterior mitral cusp ; pc, posterior 
mitral cusp ; p, posterior papillary muscle. Twice natural size. 

Fig. 12. Vertical transverse section of heart of dog in third stage of ventricular systole, to show occlusion of 
tricuspid valve — letters as in 8. (From a drawing.) Natural size. 

Fig. 13. Vertical antero-posterior section of heart of rabbit in third stage of ventricular systole, to show con- 
dition of left ventricle and mitral valve — letters as in fig. 11. SligMly enlarged. 



Trans. Roy. Soc. Edm r Vol. XXXVII. 
D r "No£L Paton on the Valves of the Heart Plate 1 . 




Fig. 1. 




rig. 2. 




Fig. 3. 



/ 





Fi§. 4. 



Fig. 5. 



'A 




Fig 6. 



M"F«.rl«,ne &Ersl<me. L>th rt Edn 



Trans. Roy 5oc. Edm r Vol. XXXVII. 
D r NOELPATON ON THE VALVES OF THE HEART Plate II. 



Fig. 7. 





l.v 




Fig. 10 



Fag. 13. 



M'Firiine & Ershme, Lu,h r ; E4m r 



( 195 ) 



XilL — A Contribution to the Anatomy of Sutroa. By Frank E. Beddard, M.A., 
Prosector to the Zoological Society of London. (With a Plate.) 

(Bead 4th April 1892.) 

Our knowledge of this remarkable genus of freshwater Oligochseta is at present 
entirely due to Dr Gustav Eisen. Within a year or two of discovering the type species, 
Sutroa rostrata* Dr Eisen found a second species, evidently referable to the same genus, 
which has been named Sutroa alpestrisA Examples of both of these species have been 
most kindly forwarded to me by Dr Eisen ; and I therefore take the opportunity of 
offering a few observations upon the structure of the genus, and upon its relations to 
other Oligochseta, as I am able, in a few matters, to supplement Dr Eisen's papers. 

The account given by Eisen of Sutroa alpestins is evidently based upon a study of 
the living worm ; it is therefore very full as regards the vascular system, but not quite 
so detailed where it concerns the generative organs, which are more conveniently studied 
by the section method. It is more especially to these organs that I desire to again 
draw attention. 

It is, however, perfectly clear from Eisen's description that the genus is correctly 
referred to the family Lumbriculidse. The contractile vascular cseca are alone sufficient 
to show this. So far as we know at present, no other family of Oligochseta possesses 
these peculiar appendages of the dorsal vessel. The reproductive organs also conform 
generally to the type met with in that family, although there are some differences in 
detail from the remaining genera of the family. 

One rather important point in the external structure of the worm is not mentioned 
by Eisen : I refer to the clitellum. Several of the specimens kindly sent to me by my 
distinguished colleague were sexually mature, and in these the clitellum was fully 
developed. I found, it to extend over nine segments, beginning with the Vllth, and 
ending with the X Vth. In longitudinal sections it was not easy to fix with accuracy the 
commencement and ending of the clitellum ; it did not either commence or end abruptly. 
As in all other aquatic Oligochseta, the clitellum consisted of a single layer of cells only. 
Those upon the clitellum differed from those upon other parts of the body by being more 
granular and by their greater depth. 

The clitellar cells were perhaps twice the depth of the epidermic cells elsewhere ; 
looking at a portion of the clitellum near to the middle, and comparing it with a 
fragment of epidermis from, say, the second segment of the body, it was quite impossible 
to confuse the characters of the epidermis of the two regions ; but the ordinary epidermis 

* On the Anatomy of Sutroa rostrata, a new Annelid of the family Lumbriculina, Mem. Calif. Acad. Sci., vol. 2, No. 1. 
t Anatomical Notes on Sutroa alpestris, a new Lumbriculide Oligocheete from Sierra Nevada, California, Zoe, vol. 
ii. No. 4. 

VOL. XXXVII. PART I. (NO. 13). 2 G 



196 MR FRANK E. BEDDARD ON 

passes so gradually into the clitellar epidermis that it is quite impossible to say where 
one leaves off and the other begins. In any case, the nine segments mentioned un- 
questionably belong to the clitellum. 

The male reproductive apparatus is very peculiar in several points — notably in the 
"prostate glands." Eisen's figure (Zoe, vol. ii., PL xiv. fig. 1) gives the general appear- 
ance of the entire reproductive system as seen when the worm is viewed as a transparent 
object. I find, however, on checking that figure by longitudinal sections, that one or two 
points are not fully shown. 

There are, as is there shown, two pairs of funnels by which the vasa deferentia 
communicate with the body cavity. They are represented by Eisen as all lying in one 
segment — the ninth. Dr Eisen reckons the prostomium as a segment; therefore, in accord- 
ance with the majority of naturalists, we may consider this segment to be the tenth. I 
find that the arrangement is not precisely as figured by Eisen. There are a pair of vasa 
deferentia funnels in the tenth segment, one on each side of the body of course. But 
the second pair, instead of lying in the same segment, are a segment further forward, i.e. 
in the ninth segment. This arrangement is more like that met with in other Lumbri- 
culidse, where one pair of funnels is in the segment which contains the atrial pores, and 
the other pair a segment in front of this. A very remarkable fact about these two pairs 
of funnels was the marked difference in size. The posterior pair were much larger than 
the anterior pair. Not only was this the case, but the tube arising from the posterior 
funnel was stouter than that arising from the anterior funnel. Concerning the opening 
of the vasa differentia into the atrium, Eisen remarks, " The exact place where the 
efferent ducts enter the atrium I have not been able to ascertain, but most probably 
this takes place in the extreme posterior part, possibly in somite XVIII." 

As will be seen from the accompanying figure (fig. 2) one vas deferens does join the 
atrium at the extreme posterior end, running alongside it up to that point ; but the 
other enters the atrium just at the point where it (the atrium) becomes invested by the 
prostates. This latter vas deferens is the stouter one, which is connected with the 
posterior funnel. The atrium itself is a long narrow tube, ciliated throughout the whole 
extent. It communicates with the exterior by a muscular penis which has been described 
by Eisen ; I have nothing to add to his description of this copulatory apparatus, except 
to say that I did not observe the glands at the external orifice. When the atrium 
leaves the penis it is coiled upon itself once or twice ; it is lined by a columnar 
epithelium, and is invested by muscular walls, the fibres of which run for the most part 
in a longitudinal direction ; from the eleventh segment onwards the atrium is loosely 
covered by a thin membrane which lies at some distance from it, and later on comes to 
be outside the prostates and the sperm-sacs. This membrane looks like the peritoneal 
investment of the atrium which has got detached. That region of the atrium which is 
surrounded by the prostates is not ciliated ; the prostates are globular masses, of which 
there were five in the individual which I examined. Eisen figures seven ; no doubt 
there is some variation in individuals. Besides, the membrane, which has already been 



THE ANATOMY OF SUTROA. 197 

spoken of as loosely surrounding the commencement of the atrium, allows plenty of room 
for the subsequent development of additional prostates. The prostates, as Eisen says, 
are composed of masses of pear-shaped cells ; the ducts of which (a prolongation of each 
cell forms its duct) open into the lumen of the atrium. 

The efferent apparatus of this worm is evidently very interesting ; it is constituted 
upon the plan of the Lumbriculidae ; but there are differences from the typical Lumbri- 
culidae. The chief difference is in the structure of the atria. In all the Lumbriculidae 
hitherto known the atria are globular sacs with a specially thickened peritoneal layer — 
occasionally termed " prostate." The same kind of prostate occurs in a genus of 
Tubificidae recently described by myself under the name of Branchiura* and also in 
the genus Moniligaster.i In both these genera the large pear-shaped cells which clothe 
the atrium externally do not communicate with the lumen of the atrium ; the prolonga- 
tions of the cells do not perforate the muscular layer which separates them from the 
epithelial lining of the atrium. Nor do they, according to Vejdovsky's figures, in 
Rhynchelmis.\ On the other hand, in the Tubificidae the " Cement-driisen " are masses 
of cells which look at first sight very much like the glandular investing cells of the 
Lumbriculidae, but are really outgrowths of the epithelium of the atrium. This has been 
proved developmentally. 

The origin of the prostates of Sutroa has yet to be studied ; but in the meantime 
they suggest those of the Tubificidae more than those of other Lumbriculidae. 

The next question is, What is the nature of the membranous sac surrounding the 
atria and the prostates ? It should be mentioned as a preliminary that this sac also 
surrounds the sperm-sacs. I think that in all probability this delicate membranous sac 
is the proper wall of the sperm-sac. The other organs only happen to lie within it, just 
as the testes lie within the sperm-sacs among earthworms. 

A year ago I communicated to this Society a paper upon a remarkable new genus 
of Oligochaata, which I named Phreodrilus; in this worm the atria and the vasa 
deferentia were surrounded by a membranous sac§ which appeared to be merely the 
peritoneal layer of the atrium and the vas deferens separated from the subjacent layer. 
The sac thus formed contained spermatozoa ; I compared this arrangement to something 
of the same kind described by Eisen in Eclipidrilus. It may be that here too we have 
a sperm-sac surrounding the atrium and the vas deferens ; but while in Phreodrilus the 
sac in question is nothing more nor less than the peritoneum stripped off from the atrium, 
in Sutroa a layer of peritoneum remains behind. 

The study of the development can alone tell us whether there is in Sutroa an 
actual splitting of the peritoneum, or whether there is a formation of a separate sac 
comparable to the sperm -sac of other Oligochaeta. 

* On the Anatomy of a new Branchiate Oligocha^te (Branchiura Sowerbii), Quart. Joum. Micr. Sci., vol. xxxiii. 
t On-some Earthworms from the Philippine Islands, Ann. and Mag. Nat. Hist., Feb. 1886. 
X Anatomische Studien an Rhynchelmis limosella, Zeitschr. f. iviss. Zool., bd. xxvii. 

§ Anatomical Description of two new Genera of Aquatic OligochEeta, Trans. Roxj. Soc. Edin., vol. xxxvi. part ii. 
No. 2. 



198 MR FEANK E. BEDDAED ON 

Apart from this matter, the efferent ducts of this worm have an interest. The 
reduction of the anterior pair of funnels and vasa defercntia suggest a commencing dis- 
appearance of these ; were they absent, the structure of the reproductive organs would be 
that of the Tubificidse ; and more especially of my genus Branchiura. In that worm 
it will be remembered that the atrium is divisible into two regions — apart from the 
terminal copulatory apparatus. The distal section of the atrium is invested by the 
prostate ; at the junction of this with the proximal half opens the vas deferens ; this is 
precisely what we should find in Sutroa; if, that is to say, the anterior pair of vasa 
deferentia were to disappear. If, on the other hand, the posterior pair of vasa deferentia 
were to vanish — of which, however, there is no indication — we should get a state of affairs 
much as is found in the more typical Tubificidse. 

I have suggested that the anterior pair of vas deferens funnels are on the road to 
disappearance ; the tube itself is very much thinner than the vas deferens connected 
with the posterior funnel ; the funnel also is in the same way much reduced. The 
comparatively large funnels which open into segment X, though spread along the 
septum, are a good deal folded. On the other hand, the funnels which depend into 
segment IX are perhaps one quarter the size of the following pair, and are not folded. 
Moreover, these anterior funnels are so far purposeless that there are no testes corre- 
sponding to them. I searched most carefully for the missing testes of segment IX, but 
to no purpose. I can therefore at the very least say that the testes if present are very 
inconspicuous ; indeed, I think that there is very little doubt as to their total absence. 

The testes are fixed by Eisen as occurring in somite X — i.e, in somite XI, according to 
the more usual enumeration of the segments in Sutroa rostrata; in S. alpestris they are 
figured (Joe. cit. PL xiv. fig. 1, tes.) as lying in the same segment as that which contains 
the penis, i.e. the Xth ; they are spoken of as being " large, and deeply and repeatedly 
lobed." 

I found, on the other hand, that the testes are not lobed in a distinct manner ; they 
are solid, almost square-shaped organs. But close to them are a pair of peculiar bodies, 
which are also found in the preceding segment. In the figure referred to as illustrating 
the reproductive system of the worm the correspondence is clearly shown : I think, there- 
fore, that Dr Eisen has overlooked the testes, and has confounded with them the peculiar 
structures already referred to as existing in the Xth as well as in the Xlth segment. 
These structures are called " albumen glands," and the duct leading to the exterior is 
figured. I am myself of opinion that these bodies (fig. 6) cannot be regarded as of a 
glandular nature ; I could find no trace of a duct, and the tissue of which they are com- 
posed is not suggestive of the glandular tissues met with elsewhere in these Annelids. 

They spring from the septa, and are, as Eisen has pointed out, of a racemose form ; 
their walls are delicate and muscular ; the contents are loosely packed cells, which are 
like the ccelomic corpuscles. They are not at all like gland cells. I should be disposed 
to compare them with the " septal sacs " so often met with in the Perichsetidae and in 
Acanihodrilus. 



THE ANATOMY OF SUTROA. 199 

The probability that these sacs are coelomic spaces, and not glandular structures at 
all, is rendered very great by the fact that on one side of the body a single diverticulum 
of the spermatotheca lay within the sac. # 

The cvaries are figured by Eisen as occurring in the XXXIInd segment. The true 
ovaries, however, lie in a more normal position ; I found them in segment XI, cor- 
responding exactly in position to the testes. They appear to be attached not only to the 
septum of that segment, but also to the cells of the vas deferens funnel. It is true that 
these supposed ovaries contained no ripe ova, so that I cannot be absolutely certain 
about the identification. Ripe ova occurred in two of the posterior segments enclosed 
within the sperm-sacs. The ova, as in all the aquatic genera, are very large, and are filled 
with spherical yolk corpuscles. 

The oviducts open on to the intersegmental groove XI-XII. In sections through 
the organ a deep cleft is seen to separate the oviduct anteriorly into two halves. 
In this has collected a quantity of debris, evidently on its way to the exterior. 

The single median spermatotheca is, as will be gathered from an inspection of 
Eisen's figure (loc. cit., PL xiv. fig. 7), very remarkable in shape. It consists of a large 
median pouch, from which arise a number of narrow tubular diverticula. Of the 
homologies of the organ, Eisen writes as follows : — " Considering this central spermatheca 
in Sutroa in connection with the two spermathecse in JRhynchehnis, two theories are 
admissible. One is, that in Sutroa one of the spermathecae has failed to develop, and 
that the remaining one has become central by being moved towards the central ganglion, 
which latter it considerably displaces. The other theory is, that in Sutroa the two 
spermathecae are represented by, or homologous with, the pairs of branched spermathecal 
sacs opening into the spermathecal atrium. The latter, then, is only an unfolding of the 
body-wall deep enough to cause the spermathecae to become merely appendices to the 
central spermathecal sac or atrium. I believe this latter theory to be the correct one." 
It seems to me that there is no need for the existence of a " spermathecal atrium." 
What has happened is, that there has been a fusion between the originally paired sacs, 
resulting in a single median sac ; in Cryptodrilus unicus we have another example of a 
similar fusion of the spermatothecse in the middle line. The spermatotheca (see fig. 5) is 
divided into two parts ; distally it is a large, comparatively thin walled sac ; the proximal 
part is a duct, with more muscular walls, opening on to the exterior. At the junction of 
the two are given off the diverticula. The existence of diverticula in an aquatic genus is 
a remarkable fact, particularly in the Lumbriculidse. They agree, moreover, with the 
diverticula of earthworms in being of a different structure from the main pouch. The 
epithelium is lower and more darkly staining ; the muscular walls are thicker. Further- 
more, the diverticula contain nearly all the sperm. This, again, is a point in which they 
resemble the diverticula of earthworms. Eisen mentions that he found in one instance 
" an interior porus in the free end of the spermatheca similar to the one described by 

Compare the enclosure of the spermatotheca of Hrjperiodrilus and Heliodrilus within a ccelomic sac (Quart. Joum. 
Micr. Sci., vol. xxxii. p. 235). 



200 MR FRANK E. BEDDARD ON 

Vkjdovsky in the receptacula seminis of Rhynchelmis limosella. The object of such an 
opening is not at present understood." In the fully mature worm the reason for the 
existence of this pore is evident ; there is in fact a direct communication ivith the lumen 
of the gut, quite obvious in sections (see fig. 5). The aperture of communication was very 
wide, and I could observe the spermatozoa in the gut itself, some bundles being partly in 
the spermatotheca and partly in the intestine. Those who are acquainted with the 
anatomy of this group of worms will recollect that this fact is by no means new. Dr 
Michaelsen was the first to show that in certain Enchytrseidse the spermatotheca has a 
similar connection with the intestine. He also was able to put the existence of this com- 
munication beyond a doubt by observing spermatozoa within the lumen of the gut ; the 
method of staining used made the matter perfectly clear. I have myself had the 
opportunity of confirming Dr Michaelsen's observations upon the Enchytraeids. More 
recently still, something of the same kind has been noted in the Eudrilidse ; of Paradrilus 
Ros8B Dr RosAt speaks as follows : — " Die beiden terminalen Schlauche der Samentasche 
setzen sich frei fort, bilden einen unregelmassigen Ring urn den Magendarm und kommen 
mit letzterem ungcfahr im 19. Segment in Verbinduno;. Es ist sehr merkwiirdig, dass 
diese Schlauche wirklich mit dem Lumen des Magendarmes communiciren, doch ist daran 
nicht langer zu zweifeln. Michaelsen sagte darueber : ' Wahrscheinlich schliessen sie 
sich (jene Schaiiche) oberhalb des Darmes zusammen ; bei dem untersuchten Exemplare 
erscheinen die beiden Enden zerfasert, wie durch einen Missgriff auseinandergerissen.' 
Bei dem mir vorliegenden Exemplare hatten die beiden Enden der Schlauche ganz 
dasselbe von Michaelsen beschriebene Aussehen. In Verbindung mit ihnen waren noch 
einzelne Stiicke des leider sehr schlecht erhaltenen Magendarmes, und man hatte den 
Eindriick als ob jene Rohren wirklich mit dem Lumen communicirten. Diesen 
Sachverhalt theilte ich meinem freunde Dr Michaelsen brieflich mit, worauf ich folgende 
bemerkenswerthe Antwort erhielt (10 Februar 1891): 'Ich habe neuerdings noch zwei 
interessante Paradrilus — Arten untersuchen konnen. An den einen habe ich, angeregt 
durch Hire briefliche Mittheilung, die Einmiindung der Samentasche in den Darm mit 
Sicherheit nachweisen konnen.' Ein solches Verhaltniss ist iibrigens nicht ganz neu. 
Michaelsen selbst hatte schon 1886 eine Communicirung zwischen Samentaschen und 
Darm bei mehreren Enchytrseiden entdeckt. Bemerken will ich noch, dass Michaelsen 
bei dicser Gelegenheit erwiihnte, dass eine Communicirung zwischen Verdauungs — und 
Geschlechtsapparat (und zwar zwischen Darm und Eileiter) schon von Ijima bei einigen 
Trematoden (Polystomum, Diplozoon, Octobothrium) beschrieben wurde. Da Zeller 
seitdem diese Angaben Ijima's fur unrichtig erkliirte, ist es hier nicht uberfliissig zu 
erwahnen, dass dieselben von Anderen Seiten wieder bestatigt worden sind, so von 
Wright und Macallum fiir Sphyranura und in neuester Zeit von Goto (in Tokio) fur 
Axine, Microcotyle, Octobothrium und Diplozoon." 

It must be, however, remembered that the so-called " spermatotheca? " of the 
Eudrilidae are not the homologues of the spermatothecse of other Oligochseta ; they are, 

" Die Exotischen Terricolen des k. k. naturli. Hofm.," Ann. k. h. naturh. Ilofm., 1891, p. 391. 



THE ANATOMY OF SUTROA. 201 

as I myself was the first to point out, # and as Kosa also showed subsequently in time of 
publication, though independently, ccelomic pouches. It has been suggested that this 
opening of the spermatothecse into the gut serves to get rid of the superfluous spermatozoa. 

It is rather remarkable that those who are on the look-out for vertebrate affinities 
among the lower animals have not fixed upon these pouches as gill-slits ; they would 
make much more respectable gill-slits than many structures which have been pressed 
into the service. 

The Nephridia, as Eisen has pointed out, have a peculiar brown body in the course of 
the tube just behind the funnel. This appears (fig. 7) to be made up of a mass of round 
cells, the borders of which are indefinable. Their nuclei are, however, quite obvious, as is 
shown in my figure. The cells are filled with round spherules of different sizes, which 
are very closely pressed together. These spherules look exactly like yolk granules. I 
could not find any lumen running continuously through this mass ; at one end a few fine 
canaliculi were visible, but they seemed to be soon lost. Among the Naidomorpha, in 
the genus Ilyodrilus, and in some other forms this glandular tract following the funnel is 
met with. In those worms, as Dr Stolc first pointed out, the swelling is permeated by 
a network of tubes. I think it very possible that the same state of affairs exists in 
Satroa ; but I have at present no certain evidence upon the point. The spongy mass of 
cells intervening between the funnel and the tube may act as a filter keeping out the 
grosser particles from choking the lumen of the nephridium. The first pair of nephridia 
lie in segment VII. There are then a number of segments without any nephridia ; they 
recommence in the XHIth segment. 



EXPLANATION OF PLATE. 

Fig. 1. Semi-diagrammatic longitudinal section through the efferent apparatus of the male organs of 
Sutroa alpedris. At., atrium ; Pr., prostate ; v.d.f., funnel of vas deferens ; T., testis ; Ov., 
ovary ; s., muscular sac surrounding the atrium and prostates, and also enclosing the developing 
sperm ; p., penis ; beyond the end of the prostates ars a series of sacs, one to each segment, 
filled with developing sperm and ova ; Vd., vasa deferentia. 

Fig. 2. Longitudinal section through the atrium and sperm-sacs. At., distal part of the atrium, enclosed 
within a delicate sac (S) ; At'., proximal part of the atrium, surrounded by the prostates (pr.), and also 
lying within a continuation forwards of the same sac ; at the upper end of the figure the peri-atrial 
sac is seen to contain developing sperm ; further forwards still (not shown in the figure) the sac 
contains only developing sperm and ova ; v.d., posterior of the two vasa deferentia, which opens 
into the atrium at the junction of the prostatic with the non-prostatic portion; v.d'., anterior vas 
deferens, opening into the atrium at its extreme end. 

Fig. 3. A more highly magnified section through the epithelium of the prostatic portion of the atrium. Ep., 
epithelium of the atrium ; pr., a few cells of the prostate ; d., ducts of the prostates ; m., muscular 

Fig. 4. Cross section through the distal part of the atrium. Ep., lining epithelium (ciliated) ; m., muscular 
coating ; p., peritoneal covering. 

* On the Structure of an Earthworm allied to Nemertodrilus, &c, Quart. Joum. Alia: Sci., vol. xxxii. p. 539. 



202 MR FRANK E. BEDDARD ON THE ANATOMY OF SUTROA. 

Fig. 5. Longitudinal section through the spermatotheca. Sp., spermatotheca opening at a into the lumen of the 

oesophagus (oes.) ; div., diverticula of the spermatotheca, filled with spermatozoa ; these are also 

shown in the main pouch and in the lumen of the gut ; 0., orifice of the spermatotheca, leading 

into the distal muscular part of the organ. 
Fi <r . 6. One of the branched ccelomic sacs attached to the septum of segment X. c, cells within the sac; 

Sp., septum. 
Fig. 7. Funnel and proximal part of a nephridium. /., funnel j gl., glandular mass immediately following the 

funnel ; n., nephridial tube. 
Fig. 8. Region of atrium illustrated in fig. 3, cut longitudinally to show muscular layer (m.) perforated by ducts 

of prostate (pr.) ; the ducts (being prolongations of the individual cells) appear as dots, among 

which are occasional nuclei. 



, s.Roy. Soc .Edm. 



M R F.E.BEDDARD ON SUTROA 



Vol . XXXVII 







2. 4 



F.E.B.del P.Smit ith 



Mint em. Bros . imp . 



( 203 ) 



XIV. — A Comparison of the Minute Structure of Plant Hybrids with that of their 
Parents, and its Bearing on Biological Problems. By J. Muirhead Macfarlane, 
D.Sc, F.R.S.E. (Plates I.-VIII.) 

(Bead 4 th May and 15th June 1891.) 



I. Introduction, 



II. 



Comparison of Hybrid Structure "with 
that of the Parents — 

(a) Philageria Veitchii, 

(b) Dianthus Grievei, 

(c) Geum intermedium, 

(d) Bibes Gulverwelli, 

(e) Saxifraga Andrewsii, 
(/) Erica Watsoni, . 
(g) Bryanthus erectus, 
(h) Masdevallia Chelsoni, 
(i) Cypripedium Leeanum. 
(k) General Observations, 

III. Comparison of the Colour, Chemical 

Constitution, Odour, Flowering Period, 
and Constitutional Vigour of Hybrids, 
with those of the parents, . 

IV. History and Structure of Cytisus 

Adami, 

V. General Summary of Results on Seed 
Hybrids, 



PAGE 

203 



207 
220 
225 
229 
232 
237 
238 
242 
245 
249 



254 
259 
270 



FAGE 

VL The Bearing of Hybridity on Biological 
Problems — 
(a) Relative Potency of the Male and 
Female Sex Elements in the Forma- 
tion of an Organism, . . . 272 
(6) Unisexual Heredity, .... 273 

(c) Bisexual Heredity, .... 274 

(d) On the Divergence of some Hybrids, " * 

or Parts of Hybrids, towards one 
Parent, 275 

^e) Mechanical or Physiological Obstacles 
to Fertilisation as an Explanation 
of Infertility in some Hybrids, . 276 

</) The Relative Fertility of Hybrids in 

Relation to Heredity, . . . 277 

iff) Vegetable Cell Structure in Relation 

to Hybridity 278 

(h) Value of Microscopic Characters in 
the Future Verification of Doubtful 
Hybrids, 281 

(i) A Consideration of the Possible 

Origin of Species from Hybrids, . 282 



I. Introduction. 

With the advance of the present century an increasing amount of attention has 
been given to the origin and relationship of plant hybrids. About 1719 Fairchild 
raised a hybrid pink from two well-known parents, but hybrids seem first to have been 
definitely recognised in the wild state, and artificially produced afterwards by Linnaeus, 
whose work induced Kolreuter to carry out those laborious and careful investigations 
and experiments which proved of the utmost value to his successors in the same field of 
inquiry. Gartner still further confirmed and extended his results, while Herbert, 
Wichura, Naudin, Naegeli, Darwin, Focke, and others have carried through detailed 
observations on groups, which are of great scientific import. 

Many gardeners and nurserymen also early realised that new forms, often of great 
beauty or striking habit, might be obtained by hybridisation, and thus a stimulus 
was given to the artificial production of hybrids. 

In 1881 Focke published his Pfanzen-mischlinge, in which I reckon that at least 
two thousand good hybrids are recorded. Many of these are of natural production, 
and their parentage may be to some degree doubtful, but a large proportion has been 
artificially produced, and the parentage is accordingly better vouched for in most cases. 

Hitherto, it may be said, observers have confined themselves almost entirely to noting 

VOL. XXXVII. PART I. (NO. 14). 2 H 



204 DR J. M. MACFARLANE ON THE 

the occurrence, artificial production, relative fertility, variability, and external appear- 
ance of hybrids. The special aim in this paper will be to compare their tissues and cell- 
elements minutely. Short synopses of my earlier results were given in the Gardeners' 
Chronicle for April and July 1890. Until after the publication of these I was not aware 
that some advance had already been made in the direction indicated, and my best thanks 
are due to Dr Masters for calling my attention to one or two publications on the subject. 

In 1831 Professor J. S. Henslow compared* a hybrid Digitalis with its parents in 
a wonderfully minute way, when we consider the degree to which histology had advanced 
in his time. He demonstrated that in the size and shape of the hairs and other structures, 
the hybrid was intermediate between its parents. Wichura t and Kerner J have proved 
that the same is true of Willows and Pulmonarias respectively. 

But to Wettstein § belongs the credit of having compared the leaves of four coniferous 
hybrids with those of the parents in general tissue arrangement. His descriptions and 
illustrations are all that could be desired, and had he carried out the comparison more 
minutely, much that is included in the present paper would have been superfluous. He 
showed from transverse sections of the leaf that each hybrid is exactly intermediate between 
its parents in the number of stomata exposed on section, the depth of the epidermal cells, 
and the number and arrangement of the sclerenchyma elements of the bundles. 

Since the publication of the preliminary account of my results in the Gardeners' 
Chronicle, a series of communications from Monsieur Marzel Branza has appeared || which 
deal, like those previously referred to, with the tissue masses only. I have not had access 
to any of the seed hybrids he describes, but one plant, Cytisus Adami, which we have both 
been able to examine, is either wrongly described by him, or its tissue and cell arrange- 
ments differ remarkably in the examples that we have each obtained. As my results 
have been drawn from detailed study of the parts of thirteen specimens, which agree 
exactly with each other, I am compelled to accept the former explanation. 

While carrying out a minute comparison of upwards of sixty hybrids with their 
parents, I have been led to adopt certain precautionary measures which must be kept 
constantly in view if one is to arrive at safe results. These are as follows : — 

(a) Average Organismal Development and Deviations from it. — It is now recognised 
by botanists that every species exhibits a sum- total of naked- eye characters which dis- 
tinguish it with greater or less precision from allied species. These are duly given in every 
local Flora. But further, specific features — alike macroscopic and microscopic — which are 
of great importance, are passed over. Radlkofer IT has already insisted that the anatomi- 
cal method must be applied to the study of species, and I have pointed out that this is 
equally true of sub-species or varieties.** But it is the sum-total or accumulation of 
minute peculiarities which gives specific identity to any organism, and it is to be expected 
that evident or naked-eye variations will often have their commencement in trivial struc- 

* Camh. Phil. Trans., vol. iv., 1833. t Bastardbefruchtung, 1865. 

I Monographia Pulmonar., 1878. § Sitz. der Kaiser. Alcad. der Wissen., vol. xcvi., 1888. 

|| Comptes Rendus, tome cxi. No. 6, 1890 ; Revue Gdnfrale de Botanique, tome i. Nos. 19, 22, 23. 

IT Akad. de- Wissenschaften, Munich, 1833. ** Trans. Bot. Soc. Edin., vol. xix., 1891. 



MINUTE STRUCTURE OF PLANT HYBRIDS. 205 

tural deviations, which, being perpetuated and exaggerated it may be in size, will ulti- 
mately appeal to the naked eye. It was this, well illustrated in the group Cirripedia, 
which forced Darwin slowly but surely to frame and enunciate his evolution hypothesis. 

As plant after plant has passed under my observation, I have been greatly impressed, 
not only with the average similarity in development that each shows, but even more 
with the constant tendency there is for individuals to vary from that average either in 
under or over development, it may be only of some small part or area, or of some large 
organ. As illustrations on a somewhat large scale, I may refer to the number, position 
on the stem, and size of leaves, a line of inquiry which has been entirely overlooked by 
systematists, but which can afford characters of considerable value. Thus Hedychium 
Gardnerianum, when well grown and not overcrowded in a hot-house, sends up flowering 
shoots which bear on the average thirteen lamina-producing leaves, beside one or two basal 
scales. H. coronarium bears twenty-one, while the hybrid, H. Sadlerianum, bears seven- 
teen. But not unfrequently from overcrowding, lack of light and nourishment, or other un- 
favourable surroundings, the number in each may be considerably reduced. Conversely, when 
very favourable vegetative conditions occur, these are accompanied with greater luxuriance. 

A shoot of Saxifraga Aizoon, with freedom for growth, produces annually twenty- 
three to twenty-six leaves ; S. Geum, forty to forty-five ; and their hybrid, S. Andrewsii, 
thirty to thirty-two. 

During the autumn of 1890 I happened to go over a large bed of sunflowers, and in 
by far the greater number twenty-seven to twenty-eight leaves were formed between the 
cotyledons and terminal capitulum. A few instructive cases of variability from the 
average were noted. The bed was one which sloped to the sun, and some plants at the 
back that were slightly overshadowed by trees had been starved in their light and moisture 
supply. Their leaves were reduced to twenty or twenty-one. On the other hand, one 
in a favourable situation produced thirty-one leaves. 

But minute changes are correlated with these grosser variations, such as an increase or 
decrease in the stomata over a given area, or in the length and number of hairs, &c. In 
the choice of material, therefore, for hybrid investigation one should either be acquainted 
with the parent individuals and the conditions under which they were grown, or try to 
choose an average specimen of each for study. 

(b) Limit of Variability. — A wide field for patient and laborious work is open in the 
direction of ascertaining how far the individuals of a species may differ microscopically 
without losing specific identity. As yet this field may be said to be untrodden,* but if we 
are to get an exact estimate alike of species and hybrid production the knowledge must 
be forthcoming. Thus Lapageria rosea is a parent form which I have chosen for pretty 
exhaustive description, and though I have tried to select material from what I regard as 
an average strain, this may still differ from the parent plant used, as several varieties 
are known to be in cultivation. This may partially explain why it is that hybrids at 

* The contributions that have recently been made (Bot. Central., Bd., xlv. xlvi.) by Schumann are exactly on the 
lines desiderated, and form a valuable study in tissue variability. 



'206 DR J. M. MACFARLANE ON THE 

times exhibit a slight divergence toward one parent. Again, I shall have to refer at 
some length to the remarkable change of colour exhibited by the flowers of Dianthus 
Grievei, from white on first opening to rich crimson or crimson-purple on fading. The 
one parent, D. alpinns, shows scarcely any trace of such floral change, but among 
the numerous varieties of D. barhatus in cultivation one exhibits the above peculiarity 
in an equally or even more striking manner. 

Now, every varietal form inherits certain common specific peculiarities, and also the 
points that stamp it as a variety, so that one would err in comparing the ordinary species 
with the hybrid. But the very fact that varieties are often inconstant in their varietal 
details, and do not hand these down in all cases so steadily as a marked species, are 
reasons for our giving a certain latitude in comparison with the hybrid, but equally are 
reasons for our desiring an exact knowledge of how far a specific form may vary. 

(c) Comparison of Similar Parts. — In my earlier investigations it was sometimes 
found that a certain part or organ of a hybrid did not exhibit intermediate blending of 
the structure of both parents, but a decided leaning to one. This was at first regarded 
as an instance of variation from average hybridity. But more careful and exhaustive com- 
parison showed that the apparently exceptional conditions arose from choice of material 
that did not agree in age, position, or opportunities for growth. Thus I stated in the 
Gardeners 1 Chronicle (April 1890) that while Saxifraga Aizoon had many stomata on its 
upper leaf surface, and S. Geum had none, S. Andrewsii resembled the latter in this 
respect. Now, I had expected to find some on the leaf chosen from the hybrid, which 
was one of the lowest of an annual shoot, those of the parents being from the upper parts 
of shoots. On returning to the matter more recently, it was found that the closely inter- 
mediate character of the hybrid was established when leaves of the same relative position and 
age were chosen. Thus, since S. Aizoon produces on the average twenty-five leaves annually, 
the hybrid thirty-two, and S. Geum forty, if the tenth leaf from the base be chosen in the 
first, we should select the fourteenth in the hybrid and the eighteenth in the other parent. 

The same principle of judicious selection of material must be applied not only in dealing 
with large organs but also in minuter details, such as bundle elements, matrix cells, and 
sclerenchyma, as well as starch grains, chloroplasts, and other cell products. 

(d) Available Limit for comparison of Parents with their Hybrid Progeny. — During the 
last decade problems bearing on the relative potency of the male and female elements in 
the development of an organism have been greatly discussed. The present investiga- 
tion not only throws great light on these, but will enable us to compare more accurately 
than hitherto the capabilities of each sex element. It is manifest, however, that when a 
hybrid is the product of parents that are widely divergent in histological details the com- 
parison will be easy, but when we attempt to compare a hybrid with two parents which 
are regarded as species, but whose chief specific differences are those of colouring and size, 
it is almost or quite impossible to detect microscopically any blending of parent characters, 
even though these may occur. Some may demur to accepting conclusions drawn from 
comparison of the hybrids of two parents that are even moderately removed from each 



MINUTE STRUCTURE OF PLANT HYBRIDS. 207 

other in affinity, particularly since we know that such are frequently less fertile than the 
pure product of either parents, or are entirely sterile. The objection will afterwards be 
considered, but here I may premise that, as a rule, whether the parents are remotely or 
closely related their evenly blended peculiarities appear, if comparison is at all possible. 

To the above general conclusion, however, we must make an important exception. 
In not a few cases, which will afterwards be cited, a separation or prepotency of the 
sexual molecules of each parent seems clearly to be indicated. 

(e) Relative Stability of Parent Forms. — Some species show both in the wild state and 
under cultivation a greater degree of stability, or want of variation tendencies, than do 
others. This is probably to be explained by an average structure having been slowly but 
steadily evolved through crossing and recrossing of an aggregate of like individuals with 
survival of those best fitted for a set of environmental conditions that remained constant 
through long periods of time. These, therefore, even when removed to rather dis- 
advantageous surroundings do not readily exhibit change. As examples, I may name 
Erica Tetralix, E. cinerea, and Philesia buxifolia. 

One finds that the opposite is equally true of not a few species. Thus, if a series of 
individuals of Geum rivale or Dianthus barbatus (cultivated) be compared microscopically, 
considerable variation is traceable. 

But even species which are considered to vary little, if compared from wide areas, 
may present unexpected changes. An interesting illustration is furnished by a plant just 
cited as one of the most invariable, viz., Erica Tetralix. I have shown elsewhere* that 
this species resolves itself into four sub-species, three of which are found in Connemara, 
and these, so far as they have been experimented on, remain true under cultivation. It 
is necessary, therefore, in the selection of a hybrid to know the exact type of each parent, 
if not the actual parent, and to examine such alongside the hybrid offspring. 

II. Comparison of Hybrid Structure with that of the Parents. 
(a) Philageria Veitchii, x . 
I have chosen this hybrid — in many respects the most remarkable yet produced — 
as the first type for detailed examination, so that anyone who has not the histological 
sympathy necessary to the task of wading through the details of other types may 
acquaint himself to some degree with the relation of a hybrid to its parents. My 
choice has been made chiefly because the walls of its elements are so evidently in- 
termediate throughout between those of its parents. It should be stated, how- 
ever, that it does not readily furnish us with illustrations of protoplasmic and allied 
modifications which less striking hybrids present. It was raised in the nurseries of 
Messrs Veitch at Exeter, by the crossing of Lapageria rosea with pollen of Philesia 
buxifolia. A very good description, with figure, was given by Dr M. T. Masters in 
the Gardeners' Chronicle^ who successfully epitomised its history in its name. For 

* Trans. Bot. Soc. Edin., vol. xix., 1891. t Gard. Chron., p. 358, 1872. 



208 DR J. M. MACFARLANE ON THE 

/. Lapagena specimens of it and parents I am greatly indebted to the Curator of Glasnevin Gardens, 

' P vSfchi? Dublin ; to the Director and Curator of the Edinburgh Botanic Garden ; to Mr Dunn of 

s. Phiiesia buxi- Dalkeith Palace Gardens ; and to Mr Laird. Both parents are indigenous to the 

western part of South America, but equally in habit, in structure, in climatic and soil 

requirements they differ strikingly. 

Lapageria rosea* grows in the forests which stretch along the lower levels of the 
Andes from Valdivia to Conception, and produces long, wiry, whip-like stems in tufted 
fashion ; these, by circumnutating movement, twine round shrubs and trees, and may attain 
a length of at least twenty-five to thirty feet. Their surface is roughly striated and 
warted, and is of a glaucous hue. The leaves when mature are about three inches long, flat, 
and leathery, exposing an ample elaborating surface to the sunlight, while the brilliant large 
flowers are produced singly or in clusters of from two to five along the upper parts. It 
delights in a clear sparkling atmosphere, and in Britain must be grown in a cool hothouse. 
Aja extremely fine variety has been brought from Southern Brazil,t and is now common 
in conservatories. It bears white flowers, but our knowledge of the flora indigenous to the 
intervening stretch of country is still too imperfect to enable us to say whether plants with 
connecting tints of flower exist there, or whether the variety is a perpetuated sport. 

Phiiesia buxifolia.\ — This is a low-growing, dense, tufted shrub attaining a height of 
from ten to fifteen inches, and throwing up hard, smooth stems of reddish-green colour 
bearing a few minute warts. The leaves are 1-| inches long by f inch wide, of a leathery 
consistence, and strongly reflexed ; their under surface also is of a dull white hue. The 
flowers at largest are about one-third to one-half those of the other parent, and the 
sepals instead of being petaloid, and nearly or quite equal to the petals in size, are of 
a dull pink-green hue and one-third the length. It inhabits the swampy, unproductive, 
wind and rain swept region extending from Chiloe southwards to Terra del Fuego. It 
eminently belies its surroundings. 

Various botanists, from Sir W. Hooker's time, have accepted these parent plants as 
types of two distinct genera ; but after minute comparison of them one is forced to the 
conclusion that they are nearly related plants which have diverged from a common type 
owing to great change in surroundings. 

Philageria Veitchii. — I cannot do better than reproduce Dr Masters' observations; for, 
apart from descriptive value, they have an interest as showing the author's views on the 
affinities of the hybrid, a matter of considerable moment when we sum up its histological 
minutiae : — 

" Messrs Veitch's plant is a scrambling shrub, with slender, cylindrical, flexuose, rigid, 
wiry, smooth, greenish branches. The leaves are alternate petiolate, about 1^ inch long 
by \ inch broad, leathery, smooth, dark shining green above, paler and marked by three 
prominent converging ribs below, oblong-lanceolate, pointed at the apex, and with a 

* Kunth, Enum. Plant., v. 283 ; Adans., i. 44 ; Bot. Mag., vol. lxxv. tome 4447 ; vol. lxxxii. tome 4892 ; Ball, 
Jour. Linn. Soc, vol. xxii. pt». 162-166. t Bot. Mag., vol. lxxxii. tome 4892. 

I Darwin, Voyage of the Beagle ; Kunth, Enum. Plant, v. 284 ; Hooker, Flora Antartica, vol. ii. p. 355 ; Bot. 
Mag., vol. lxxix. tome 4738. 



MINUTE STRUCTURE OF PLANT HYBRIDS. 



209 



cartilaginous, very finely serrulate edge. The leaf-stalk is about -| inch long, convex 
below, flattened above, transversely jointed in the middle. The flower-stalks are axillary, 
about the length of the petiole, and bear numerous overlapping glabrous bracts, ovate- 
concave in shape, and increasing in size from below upwards. The flower is solitary, 
pendulous, with a calyx of three fleshy, glaucous, pale rosy-purple, oblong-lanceolate, 
boat-shaped sepals, and a corolla of an equal number of fleshy, bright rose-coloured 
petals, which are slightly unequal in size, overlapping, broadly ovate-acute, with a 
circular honey pore on the inner surface at the base. The stamens are six in number, free, 
hypogynous or attached at the very base of the segments of the perianth, and a little 
shorter than the petals. The filaments are fleshy, subulate, pink-spotted. The anthers 
are about \ inch long, yellow, linear-oblong, two-celled, dehiscing by a longitudinal 
chink at the side, tubular at the base, so that the extremity of the filament is concealed 
at its point of insertion by a kind of sheath ; pollen scanty. The ovary is about \ inch long, 
elliptic, glaucous, one-celled, with three parietal placentae, and surmounted by a columnar 
style, which slightly exceeds the petals in length, and is terminated by a triangular 
capitate stigma. The ovules are numerous and anatropal." 

" Such is the description of this hybrid production. Hybrids between two genera are, 
to say the least, uncommon, and it may be that some will consider this hybrid as a proof 
that Lapageria and Philesia constitute not two, but one genus. To us, however, it 
seems, with a due appreciation of the arbitrary character of many of the so-called dis- 
tinctions between genera, that the two genera in question are as distinct as two such allied 
groups can well be. Lapageria has a regularly six-parted perianth, and free stamens : 
Philesia has a distinct calyx and corolla, and partially inseparate or monadelphous 
stamens. Lapageria is a climber: Philesia an erect shrub." 

" In habit our plant is, of the two, more akin to the female parent (Lapageria) than to 
the male. Its foliage is singularly intermediate, but at the same time nearest like that 
of the pollen parent (Philesia). In the characters of the flower-stalk, calyx, and corolla, 
it is more like Philesia than Lapageria, but in the stamens it approximates to the 
mother-plant, and diverges from the characters of the male. In colour it is also more 
like the mother-plant than it is like Philesia. The fruit we have not seen." 

" The characteristics of both parents are so curiously blended that we fear this plant 
will not lend much aid to those investigators who are striving to determine what is the 
effect on the offspring of pollen or seed parent respectively. On the whole, it would seem 
as though the organs of vegetation, including the calyx and corolla, were more like those 
of the male (Philesia), while in the stamens and pistil the progeny ' favour the mother.' ' : 

I have chosen for description the largest, oldest, and most mature material available ; 
and, unless otherwise stated in the text, it is from this that preparations have been made 
throughout.* 



1. Lapageria 

rosea. 

2. Philageria 

Veitchii. 

3. Philesia buxi 

folia. 



* In all succeeding descriptions the names of parents and hybrids are printed at the top of each page, and numbered 
in italics. The seed parent, if determined, is in all cases 1, the hybrid 2, and pollen parent 3. For brevity these 
numbers are used in the text. 



210 DR J. M. MACFARLANE ON THE 

'. Lapageria Root. — Transverse sections of the root of 1 (Plate I. fig. 3) show that the epidermis 

t. Phiiageria s00n ruptures, and is destroyed by abrasion or is shed in patches. Where tracts of it 
>•. Phiiesia buxi- are l e ft like the one seen in the figure, the cells are equilateral or columnar in outline with 
more or less rounded angles, and measure 40 /x across. A considerable degree of variability 
is shown in the outline of these, and this is in striking contrast with corresponding cells 
of 3, which are very uniform. As might be expected from its duration, and as is proved 
when soft young roots are examined, the cuticular layer is always thin. The epidermis of 
3 is strongly persistent (Plate I. fig. l), and is made up of cells which are one and a half 
to two and a half times broader than deep, measuring 80 by 60 /x on the average. Each 
has a very thick cuticle on its outer face, which is continued as a thinner layer inwards 
between adjoining cells, and the cuticular lamellae are very evident. Large unthickened 
areas, with pore apertures, occur over the transverse partitions. In 2 the epidermis (Plate 
I. fig. 2) persists well on the whole, though here and there one finds areas over which 
rupture and decay of cells has begun. Each cell is from equilateral to columnar, but 
considerable variability is shown, thus the cells in the figure are slightly columnar, but 
others in my possession are decidedly more like those of 3. But a very constant feature 
is the amount and disposition of cuticular substance. As shown by comparison of 
figs. 6, 5, and 4, the amount is about half of the parent extremes, and is thickest externally, 
thinning out round the sides. On the transverse partitions are unthickened areas 
that show smaller and more minute pores than in 3. 

The outer cortex of 1 (fig. 6), to the extent of eight to ten layers, is greatly thickened 
in its elements, by sclerenchyma deposits, of which the external three or four zones are 
smaller in size and more thickened in their walls than those internal. The latter pass, 
by a pretty gradual transition, into the large-celled parenchyma of the inner cortex. 
The average size of the sclerenchyma elements is 20 /*-. In 3 the outer cortex (fig. 4) 
is strongly thickened only in the sub-epidermal cell layer, each element of which has a 
greater amount of thickening over its outer than over its lateral faces, and measures 60 \i. 
across. Beneath this are one or two layers very feebly thickened and smaller than the 
last (40 to 50 m), which are demarcated abruptly from the thin-walled large-celled paren- 
chyma. In 2 (fig. 5) four to five layers are thickened, and of these the external one is 
made up of rather larger cells which show a greater thickening of their outer than of their 
lateral walls. The cells measure 32 to 35 /a across, and are continuous, by a row of transi- 
tion cells, with the inner large-celled parenchyma. 

The inner cortex of 1 is a cylinder of twenty to twenty-five cell layers, the average size 
of the elements being 45 to 50 /x. The two or three innermost layers next to the bundle- 
sheath are shallow and flattened. That of 3 is a cylinder of eight to nine open loose- 
looking cell layers, the cells of which are 100 to 120 /x across. Only the innermost layer 
may be slightly smaller but not flattened. In 2 the cylinder consists of fifteen to seven- 
teen layers whose elements are 70 to 75 /a ; the innermost layers are flattened, and the 
one external to it smaller in its cells than those of the general cortex. 

The bundle-sheath is of considerable interest. In 1 (Plate I. fig. 9) it consists of small 



MINUTE STRUCTURE OF PLANT HYBRIDS. 



211 



isodiametric cells 18 to 20 xi across; their walls are thickened by five to six lamellae, 
which enclose a circular or oval lumen (fig. 10c). In 3 (fig. 7) the cells are radially 
elongated, measuring 48 to 50 /x in radial direction, and 35 to 40 /x tangentially, so that 
each cell is barely one and a half times deeper than wide ; there are eleven to twelve 
highly refractive lamella?, while the almost obliterated lumen of the cell is an elongated 
slit (fig. 10a). In 2 (fig. 8) the cells are mostly elongated radially, though rarely one 
finds a nearly isodiametric cell ; they measure 35 /x in depth and 20 to 22 /x in width. 
Each has eight or nine lamellae, which are less refractive than in 3 (fig. 106). 

The pericambium in all is very much alike, and its constituents soon undergo 
thickening and conversion into permanent tissue. 

The phloem patches of 1 (fig. §ph) vary from twenty-three to twenty-eight in all 
mature roots examined ; those of 3 are eight to ten in number ; while in the hybrid there 
may be seventeen to twenty patches. 

The xylem of 1 has its wood tracheids most strongly thickened in a circular area 
which extends round internal to the phloem, while the radiating xylem spokes show pretty 
large spiral tracheids. The centre consists of cells that are slightly thickened, and which 
form a root pith. The pitted vasa are large, numerous, often disposed in groups of 
two to three, and average 60 /x across. The xylem of 3 shows thickest tracheids in the 
middle, with narrow, irregular radiating spokes passing out between the phloem patches. 
One pitted vas, or rarely two, occurs in the angle between each pair of phloem patches, 
and measures 37 to 40 /x across. The xylem of 2 is made up of tracheids pretty uniformly 
thickened, or rather less so internally than externally ; the pitted vasa are more numerous 
than the phloem tracts, and are occasionally grouped in pairs, very rarely in triplets. 
Each measures 48 to 50 /x. 

The root, therefore, is very exactly intermediate in the tissues outside the bundle cylinder, 
but the cylinder itself slightly diverges towards the seed parent in some of its features. 

[I do not refer in detail here to longitudinal views of the root elements, as they 
fundamentally resemble those of the stem, which will now be examined.] 

Stem. — The descriptions of this have been taken from preparations made at a level of 
one inch above ground. As already stated briefly, the glaucous stem of 1 is roughened 
both by longitudinal ridges and by a close-set series of wart-like papillae, that are often 
cut through in transverse sections. The stem of 3 is quite smooth, except that here and 
there minute warts similar to those of 1, but greatly reduced in size, are sparingly pre- 
sent. In the hybrid, as we shall see, there is a very exact blending of the two conditions. 

Transverse and longitudinal sections of 1 show epidermal cells whose free surfaces are 
traversed by four to six of the ridges above mentioned, each measuring 5 /x in depth 
(Plate II. figs. 3,6). The cells have grown out in a part of the figure cited, so as to form 
one of the papillae which are distinguished with the naked eye. Each cell is isodia- 
metric or slightly columnar, and while the outer surface is strongly cuticularised the lateral 
faces are little altered. The average size of each is 60 /x long by 35 /x wide and 40 /x 
deep. In 3 the free faces of the cells are quite smooth (figs. 1, 4), and the thick cuticle is 

VOL. XXXVII. PART I. (NO. 14). 2 I 



Lapageria 

rosea. 
Philageria 

Veitchii. 
Philesia buxi- 

folia. 



212 DR J. 3J. MACFARLANE ON THE 

1. Lapageria proportionately in depth as 4 to 3 in Lapageria. Each cell is tangentially flattened, 
-• Phiiageria an d the cuticular layer is continued inwards in wedge fashion along the lateral walls. 

Veitchii. J . 

s. Phiiesia buxi- Its average size is 100 ft long by 30 ft wide and 25 ft deep. In 2 the free epidermal cell 
faces have ridges 2^ to 3 ft deep (figs. 2, 5). Each cell is intermediate in shape, and 
measures 80 ft long by 30 ft wide and 35 ft deep. It should be said, however, that while 
this is the average of many measurements, the cells are variable in size. The cuticle 
dips in along the lateral walls in wedge-like fashion as in 3. 

The outer cortex in 1 is made up (fig. 3) of twenty to twenty-five layers of large, 
moderately thickened cells, which pass abruptly into an inner cortex of fifteen to twenty 
layers of dense sclerenchymatous cells nearly or quite uniform in thickening and trans- 
lucency. Each cell wall of the latter elements shows four to five thickening lamellae. 
In 3 (fig. 1 ) the outer cortex consists of nine to ten layers, the cells of which are larger and less 
thickened than in the last. The inner cortex shows three to four indurated layers, of which 
one or two external are greatly thickened and brown pigmented, the internal ones having 
clear and less thickened walls. The former exhibit eleven or twelve thickening lamellae. In 
2 (fig. 2) there are fifteen to seventeen layers in the outer cortex, and in the inner nine to 
eleven. The outermost cells of the latter are slightly pigmented brown if mature stems 
are chosen near the level of the ground. Each wall has seven to nine thickening lamellae. 

Longitudinal views of the three demonstrate that there is a very pretty intermediate 
condition in the hybrid between the numerous and distinct wall pits of the outer cortex 
in 1, and the few and faintly-marked pits in 3. 

The central parenchyma of the stem is small-celled, thick-walled, and pretty uniform 
in 1 ; that of 3 is large-celled, thin-walled, except for a few isolated and more strongly 
indurated elements scattered irregularly. The hybrid is very closely between these 
conditions. In longitudinal view the relative amount of thickening and distribution of 
the wall pits is equally noticeable here as in the outer cortex. 

Vascular Bundle System. — The stem bundles appear in all cases to be greatly larger 
in 1 than in the other parent or hybrid, the average diameters being as 400 ft in 1 to 
250 ft in 2, and 180 to 200 ft in 3. If, therefore, the hybrid material was sufficiently 
matured, it approaches here to the pollen parent. 

In 1 the phloem patches (fig. 9) are 85 to 90 ft deep, and are made up of large sieve- 
tubes, each 40 to 45 ft across, along with others that are smaller but of varying size ; also 
of companion cells 8 to 10 ft across. The xylem has a flat or slightly convex face next the 
stem centre, and its main mass is made up of two large scalariform vasa. # Each vas is 100 
to 120 ft across, and between each pair are smaller radially- elongated scalariform or pitted 
vasa (or tracheids), and in line with the front of the vasa is a small protoxylem patch. 

In 3 the phloem patches (fig. 7) are 45 to 50 ft deep, the sieve-tubes are nearly uniform 
in size, unlike those of 1, and measure 20 to 25 ft across, while the companion cells are 5 to 
8 ft. The xylem is typically wedge-shaped, the back part next the phloem being occupied 

* I ii compound or branching bundles several of these, usually of smaller size, may represent the above, and the same 
is true regarding the others treated of. 



MINUTE STRUCTURE OF PLANT HYBRIDS. 



213 



on each side by two scalariform vasa 50 to 70 /*, across, and dense, thick-walled tissue unites l 
them. In front are scalariform or pitted tracheids, which project inwards to form the 2 
greater extent of the xylem wedge. The innermost part of the wedge consists of a 
transversely elongated mass of protoxylem tissue. 

In 2 the phloem patches (fig. 8) are 50 to 60 /x deep, the sieve-tubes are 25 to 28 /x across, 
and the inner are rather larger than the outer, while the companion cells measure 7 to 9 //.. 
The xylem is not so deeply wedge-shaped as in 3 ; the scalariform vasa are 75 to 85 fx across, 
and are united by slightly indurated cells, in front of which are radially-elongated scalari- 
form and pitted tracheids, while a small oval protoxylem patch completes the bundle. 

Leaf. — The petiole in parents and hybrid is divisible into a lower, flattened-out, and 
concave region, in whose axil a cone-shaped bud develops. This is very closely protected in 
Philesia by the concave petiole base bending up in knee-like manner round it ; in Lapageria, 
however, and to a less extent in Philageria, the bud is well exposed. The upper petiolar 
region, which extends beyond the level of the bud apex, is usually plano-convex, or a 
groove mav traverse the flat face of it. 

These two regions are characterised by marked histological differences ; the matrix 
cells of the lower part are only moderately thickened, but many of the upper are so 
thickened as to become hard stone cells. 

The epidermis of the three agrees with that of the stem, except that in Philesia the 
cuticular surface shows ridge-like stria? 1 ju or less in height, as compared with those of 
Lapageria, which are 3 to 4 fi, and of Philageria, which are 1^ to 2 /a. That this structural 
feature should be general in Lapageria, and only traceable over the leaf of Philesia, 
affords strong evidence of their near relationship. 

Considerable variety exists in the distribution of the stone cells in the upper petiolar 
region, but on the average few occur just beneath the epidermis in 1, though they are 
massed as an indurated matrix round the central bundles. In 8 the entire circum- 
vascular matrix is dotted over by stone cells, which, after staining and decolorising, are 
very sharply differentiated from the unthickened cells. In 3 the distribution is evenly 
intermediate, in some leaves examined, in others a massing towards the centre, as in 1, 
predominates. 

Seven bundles, or rarely five, run through the petiole in 1 ; five bundles are usual in 
f ; three, with at times two smaller ones, occur in 3. The size and number of sieve-tubes, 
vasa, and tracheids are closely intermediate in the hybrid. 

The lamina may fairly be regarded as the most instructive part of the plant, for one can 
scarcely desire to encounter greater diversity in two parents than is here shown in size, 
form, consistence, and structure, while a more exact blending of these in the hybrid could 
hardly be expected. 

On surface view * the upper epidermis of 1 shows cells of varying size (Plate III. fig. 6), 
but with white wavy refractive walls. Though the majority are of a radiate type, it is 

*■ For preparations of the epidermis and other parts, as also for similar preparations of other species, the potash method 
of maceration has proved invaluable (Proc. Brit. Assoc, Aberdeen, 1885), since it enables one to get clean and large areas 
for examination.1 



Lapageria 
rosea. 

2. Philageria 
Veitchii. 

3. Philesia buxi- 



folia. 



214 DR J. M. MACFARLANE ON THE 

' L rwfa ena no ^ "uncommon to find elongated cells over the veins. The lower epidermal cells (fig. 9) 
-• p ^ ll * g t" a ^'e more sinuous in outline, thinner in their walls, and of smaller size. The stomata 

veitckii. ' 

5. Ph ( j 1 1 i ? 8ia buxi - which lie amongst these are irregularly disposed and freely exposed on the surface. Under 
Zeiss' D objective with 4 eyepiece, ten to eleven are seen over the field. The upper epidermis 
of 3 shows cells of varying size, but with straight, yellowish, and thick walls, abundantly 
traversed by pore canals. The lower epidermis has to the naked eye a whitish waxen 
appearance, and this is found from microscopic study to be due to extremely minute 
wart-like papillae that are deepest over the outer area of each convex cell surface. 
The presence of these breaks up and diffuses the light. They are not wax excretions 
since they are unaltered by all wax tests ; neither do they appear to be pure 
cuticle, though their persistence in an unaltered state after many chemical tests suggests 
a peculiar modification of cuticle. I have at times noticed on surface view what seemed 
to be the homologue of them in Lapageria, though of extreme fineness, but vertical 
sections have as yet failed to reveal their undoubted presence. 

It occurred to me that this peculiar formation in PJdlesia might be a development 
suiting it to climatic surroundings, and that other genera from the same region might agree 
with it. The first plant selected for comparison was Astelia racemosa, which is very 
different in its general features though included in the same natural order. Its lower 
leaf epidermis showed exactly similar surface formations, so that a further examination 
of plants from the same region is highly desirable. 

The lower epidermal cells of 3 (fig. 7) have strongly convex surfaces, are straight 
walled, and, as pointed out by De Bary, # the stomata are in rows, while " the slits run 
perpendicular to the axis " of the organ. They are so deeply sunk, however, that the 
guard cells are entirely hid, and the stomatic orifice is seen as a faint slit in the 
depression between adjoining epidermal cells. Commonly one stoma alternates with 
each epidermal cell, so that thirty-two to thirty-four are visible under Zeiss' D with 
4 ocular. 

The outline of the upper epidermal cells of 2 in some specimens examined were 
decidedly more like those of 3 than 1 (Plate III. fig. 5), the waviness of the walls being 
very slight, and the thickening considerable ; but even in such, one could readily trace 
the effect of Lapageria parentage if preparations of the three were placed side by side. 
In other material, however, the outline was as exactly intermediate as if one had 
attempted carefully to draw it so. This is one of the many examples which one constantly 
encounters of variability in a hybrid, as in species, and demonstrates the need of exact 
comparison as to age, position on the stem, food supply, &c, for I believe that consideration 
of such points probably explains the apparent discrepancy. 

Apart from this, however, it is generally to be noticed that both upper and lower 
epidermal cells of the hybrid are equal to, if not larger than, the largest of either parent. 
Those of 1 are on the average larger than those of #, but in the hybrid they may be larger 
than in either parent. Now, from Kolreuter's time onward, the increased luxuriance of 

* Cornp. Anat. Phan, and Ferns, Eng. ed., 1884, p. 45. 



MINUTE STRUCTURE OF PLANT HYBRIDS. 



215 



some hybrids over either parent has arrested attention, and it has been accounted for by 
supposing that the strength which is not spent in fruit production passes into the vegetative 
parts. For many reasons this can scarcely be accepted as a true explanation, and the case 
now adduced leads us rather to believe that its cause is to be sought for in some deep-seated 
cell condition which exists before the reproductive organs have appeared. Evidence 
could easily be adduced to prove that it as often exists in fertile as in sterile hybrids ; 
probably even more so in the former, if my data give a true index to the entire range 
of hybrids, while Focke shares the same opinion.* I would suggest that an explanation 
is to be had rather from the standpoint of exaggerated cross-fertilisation effects, and 
that increase of the hybrid over the parents is due to increase in size of cells rather 
than to increased multiplication of them. 

The lower epidermis (Plate III. fig. 8) is very neatly intermediate in shape of the 
cells and disposition of stomata. The former have a waviness derived from 1, but also 
a transverse extension usually which is derived from 3. The stomata, though 
partaking somewhat of the irregularity of 1, can readily be followed in undulating 
lines as in 3. But under the same area as above there are only eighteen to twenty 
stomata, which would be explained if we take into account the increased size of the 
epidermal cells. At the same time such a distribution suggests points of great com- 
plexity relating to transpiration, &c, which we cannot here enter into. 

I would draw attention, however, to the cuticular warting, which is, as nearly as one 
can measure, half as strongly developed as in Philesia, and, like that parent, is most 
strongly formed on the slightly arching sides of the epidermal cells. 

Several authors assert that there are fundamental differences in the leaf venation of the 
parents. Eeference to Plate III. figs. 3, 2, and 1, will show that both are modifications 
of a common fundamental type, and that the hybrid exactly connects them in distribution 
of the large and small veins alike. The leaf venation, in truth, coincides with other parts 
in teaching us that Lapageria is a form specialised for living under mild environmental 
conditions, while Philesia is equally specialised for rigorous atmospheric surroundings. 
The reduction in the number of longitudinal vascular bundles in Philesia, their greater 
size and strength, their firm union at the apex, the strong nature of the transverse or 
oblique girders, and their reduction in number, all point to derivation from a type 
nearly like the hybrid, and that alteration has occurred to suit the 'peculiar climatic 
surroundings which Darwin, Agassiz, and others have depicted as existing on the 
"West Fuegian coast. 

Transverse sections of 1, taken at equal distances from apex and base of the leaf, 
show that the epidermal cells just over the median vascular bundle, though narrower than 
the average of those over the leaf surface, are quite as deep. They are separated from the 
indurated sheath of the bundle by one or two layers of rounded cells continuous with those 
of the palisade parenchyma. In 3 the epidermis over the median bundle is depressed, and 
its cells are greatly reduced in width and depth, so that they form a median line very 

* Pflanzen-mischlinge, p. 475. 



1. Lapageria 

rosea. 

2. Philageria 

Veitchii. 

3. Philesia buxi- 

folia. 



216 DR J. M. MACFARLANE ON THE 

i. Lapagena different from the epidermis over the lamina. These small cells abut directly against the 

rosea. r jo 

;. Phiiageria indurated elements round the bundle, so that the palisade parenchyma of the leaf is sharply 
?. piniesia buxi- interrupted in its continuity along this line. In % the female parent is more nearly 
approached, but a slight flattening of its epidermal cells occurs, and the cells con- 
tinuous with the palisade layer become shallower above the indurated sheath. 

In 1 the parenchyma beneath the sheath and next to the lower epidermis is largely 
developed, there being four to five layers of rounded, loose-looking, and often thick- walled 
cells. In 3 a single layer only occurs beneath the bundle, and its cells are thin walled, 
while in 2 there are two to three layers, and some of the cells in these are slightly 
indurated after the type of 1. 

The upper mesophyll of 1 is made up of three to four palisade cell layers, which, 
however, scarcely deserve the name in its ordinary application, as the cell elements 
are quadrangular or isodiametric. They measure on the average 35 //. in depth and 
width. The intercellular spaces between these are of considerable size. The spongy 
mesophyll is one and a quarter to one and a half times as deep as the upper, and is 
composed of rounded or branching cells separated by cavernous intercellular spaces. In 
old leaves the walls may be strengthened by reticulate or hoop-like secondary deposits. 
The mesophyll of 3 is made up of two palisade cell layers, which pass by abrupt transition 
into a dense spongy lower zone. The cells in the uppermost of the two palisade layers 
are closely packed, and are three and a half times deeper than broad, those of the lower 
are two to two and a half times deeper than broad, the former measuring 110 by 30 [x, the 
latter 75 by 35 /a. The cells of the spongy zone are very irregular in shape, usually 
closely pressed against each other, but may have small cavernous spaces. In 2 the two 
uppermost layers are clearly defined as a palisade tissue, and traces of a third may 
be distinguished. The cells of the top layer are 70 to 80 /a deep by 35 [x wide, and those 
of the subjacent one 50 to 60 fx deep by 35 /x wide. Though fewer and smaller than in 
the parent, intercellular spaces like those in 1 occur between the walls of the palisade cells. 

The median vascular bundle with its indurated sheath is in the proportion of 10 in 1 
to 9 in the hybrid and 8 to 8^ in 3, but the relative size and amount of tissue components 
differ strikingly. In 1 the masses of sheath tissue and of bundle tissue are nearly equal in 
amount ; in % the sheath tissue is considerably in excess of the bundle tissue, the propor- 
tion being as 1\ or 3 : 1 ; while in 3 the sheath is strongly developed, and is in proportion 
to the bundle as 5 : 1. The indurated cells in 1 are thick walled, isodiametric, and uniform 
with each other, measuring on the average 20 [x across. The vascular bundle tissue is oval 
or circular in outline, and its main mass is made up of wood vasa and tracheids, the largest 
of the former being 20 /x across. The indurated cells of 3 are mostly large round the periphery, 
and measure 37 to 40 ll across, the inner are densely-packed, small, thick-walled cells, 
irregular in shape, and dissimilar with each other, but the average measurement is 
20 to 25 /x across. The small bundle is lanceolate in outline, with wood scarcely larger 
than bast, and the largest vasa measure 10 to 12 fx across. In 2 the indurated cells are 
larger externally, where they measure 30 to 32 [x ; internally they are denser and average 



MINUTE STRUCTURE OF PLANT HYBRIDS. 



217 



20 to 22 fi. The wood approaches more nearly in outline and disposition that of 1, while 
the largest vasa are 15 to 16 /x across. 

The lateral bundles, which run along the leaf margin in the three, exhibit the above 
peculiarities in an even more accentuated manner. 

Equally interesting, as in the petiole, is the occurrence along the leaf margins alike 
in parents and hybrid of cuticular ridges, each of which is 4 fx in 1, 3 fi in 3, and 3 to 3^ /u. 
in #. It will thus be seen that along the leaf margin in Philesia the ridges are more 
developed than on the petiole, and approach very closely to what one finds in Lapageria. 

Sepals. — The large crimson fleshy sepals of 1 are nearly or quite the length of the 
petals in most cases, but I have gathered blossoms on three occasions in which they were only 
about two-thirds as long. This is of some little importance as showing that there is consider- 
able tendency to reduction in the length of the sepals compared with the petals. At the base 
of each, and between their lateral attachments to the receptacle, is a large, deeply-excavated 
nectar-cavity shown in median longitudinal section in Plate III. fig. 12. On transverse 
section it is shaped like the letter \J, except that the arms are more diverging, and from 
the vascular bundles which run up into the sepal many branches pass inwards and are 
richly distributed beneath the gland tissue. The gland, which is a convex pad-like 
cushion, consists of a surface epidermal layer, the cells of which are greatly smaller and more 
richly protoplasmic than ordinary epidermal cells, while beneath are twelve to thirteen 
layers that are more irregular and variable in outline. I have counted several carefully 
selected gland sections, and find that these show 170 cells in length, 50 in'width, and 13 
deep on the average, or a total of about 1 15,000 cells. In 3 the green or reddish-green sepals 
are at most one-third the length of the reddish-pink petals ; each is thin, slightly membran- 
ous and inserted by a narrowed base into the receptacle. As shown in Plate III. fig. 10, 
there is no trace of gland tissue, while the simple vascular bundles form no inferior plexus. 
On transverse section it is convex externally. In 2 the sepals are greenish red, about one- 
half to five-eighths the length of the petals, and rather fleshy in consistence. Each has at 
its base a honey-gland (fig, 11), which is a raised cushion-like mass as in 1, and on trans- 
verse section is semilunar, or nearly sickle-shaped. A rich plexus of vascular bundles 
ramifies beneath it. The gland shows, as nearly as can be estimated, 90 to 95 cells in long 
direction, 50 across, and 10 deep, or a total of about 45,000 to 48,000 cells. When one 
thinks of the extreme difficulty of exact estimation here, too great stress can scarcely be 
laid on numbers, but that the bulk of the gland is almost or exactly half that of Lapa- 
geria one recognises when each is isolated. It may be safely inferred here, therefore, 
since many other cases confirm it, that the reduction of the hybrid gland by half is due 
to actual reduction in number of cells. 

On surface view the upper epidermal cells in 1 are as broad as, or broader than, long, 
while the walls are very thin and delicate. In 3 the cells are irregularly elongate, and 
have thickened walls penetrated by evident pore canals. In 2 the cell shape and wall 
thickening incline rather to Lapageria, but the effects of Philesia, action are quite pro- 
nounced. 



Lapageria 

rosea. 
Philageria 

Veitchii. 
Philesia buxi- 

folia. 



folia. 



218 DR J. M. MACFARLANE ON THE 

/. Lapagena >phe m esophyll substance agrees with that of root, stem, and vegetative leaf in that 

8. Phiiagena its cells are smallest in 1, largest in 3, and intermediate in 2 ; but, further, Philesia has 

Veitchn. ° 

* P iv!if,? ia buxi " brown pigment cells of varying size, which are well shown in fig. 10. I have failed to 
find traces of these in the hybrid, though we shall see that they appear in the petals, 
beiuij inherited from those of Philesia. 

Petals. — In 1 the honey-gland is developed at the bottom of a rather deep pouch, the 
opening of which is seen between the bases of the stamens, and these cover the gland cavity 
over two-thirds of its area. In longitudinal section its upper part protrudes suddenly from 
the petal surface, and forms a thick pad which gradually tapers out below. At its upper 
thickest portion it consists of nineteen to twenty-one cell layers deep. The vascular bundles 
distributed to the gland are arranged in a rather loose and open manner, one set of bundles 
— the gland bundles proper — lying immediately beneath the gland tissue, the remainder, 
from which the former are given off, lying external to, and in most cases alternate with 
them. In 3 the gland is a nearly circular pad of tissue lying exposed at the base of the 
petal, and though on longitudinal section it swells out rather abruptly above, it retains a 
very uniform depth throughout till near its base. The greater mass of the gland is 
composed of ten to eleven cell layers, and beneath the whole the vascular bundles are 
densely arranged side by side, or obliquely beside each other. In 2 the gland is in every 
respect intermediate, for I have failed to find any feature in which it specially sways to 
either parent. 

The external epidermal cells in the three greatly resemble each other, but when one 
turns to the inner surface those over the upper part and down the middle towards the 
base of the petal in 1 are mostly broader than long, though at the edges they are 
equilateral, or longer than broad. In 3 the cells at the top are mostly twice as long as 
broad, while below they become even more elongated proportionately. The hybrid cells 
are intermediate. One does not find cells in Lapageria with brown granular contents 
such as occur on the sepals and petals of Philesia : but though absent on the sepals so far 
as I can trace, they are present in the petals of the hybrid, though the contents are paler. 

Stamens. — I have not attempted to compare minutely either stamens or carpels, but 
the pollen grains have been examined with care. In both parents the pollen cells are 
spherical, echinated, and well formed in good flowers, those of Philesia being slightly larger 
than those of Lapageria. The cells of the hybrid, however, are to all appearances bad 
to the extent of at least 95 to 98 per cent. They are very irregular, small, shrivelled, and 
starved-looking shells ; a few approach in size and form to those of the parents, but only 
two or three in a hundred are at all well formed. I should consider, therefore, that 
attempts to recross this hybrid would be attended with great difficulty. No com- 
parison is made of the more vital parts in Philageria or its parents, since the very 
pronounced character of their cell walls militate against convenient examination of the cell- 
contents ; but the careful manner in which moleeule has been added to molecule in these 
walls, proves that the building substance or protoplasm which has accomplished this work 
in the hybrid must be an intimately blended product of that of the parents — i.e., that 



MINUTE STRUCTURE OF PLANT HYBRIDS. 



219 



the male element or fertilising cell of the pollen grain and the female element or egg-cell 1 
of the ovule have equally contributed to the rearing of the hybrid organism. 

But to quit now our consideration of Philageria as a hybrid, it may possibly 
possess an interest in the future from the standpoint of species evolution. That Philesia 
and Lapageria are closely-related forms cannot well be doubted from what we have 
already seen of their histological details. The older botanists, guided only by naked-eye 
characters, considered that the parents well deserved to be rauked as genera. The latest 
advocate of this view was Sir William Hooker, but his distinguished son, Sir Joseph 
Hooker, thus expresses himself in his Flora Antarctica : — " With regard to the genus 
Lapageria, it is so closely allied to Philesia that I doubt its validity, the chief differences 
being the nearly equally-divided perianth of Lapageria, its more distinctly three-lobed 
stigma, oblong berry, twining branches, and differently nerved leaves, in all which respects 
it is more evidently a genus of Smilacece than either Callixene or Philesia." Now, in 
all of these features, except the twining nature of the stems, I have noticed examples of 
Lapageria which tend to break down the generic distinctions. 

Thus the nearly equally-divided perianth in Lapageria is not invariable nor is the 
fusion of stamens, while the figures of leaf- venation prove that both are fundamentally the 
same. Therefore we believe that the differences in the parents may largely be explained 
as modifications on some original common type brought about to suit the greatly altered 
environmental conditions. Here I may be allowed to quote the opinion of the late John 
Ball, F.R.S. : # — " The true explanation, in my opinion, of the exceptional poverty of the 
Patagonian flora is to be sought in the direction long ago indicated by Charles Darwin, 
when, in discussing the absence of tree-vegetation from the Pampas, he remarks that in 
that region, recently raised from the sea, trees are absent, not because they cannot grow 
and thrive, but because the only country from which they could have been derived — 
tropical and subtropical South America — could not supply species organised to suit the 
soil and climate. So it happened in Patagonia — raised from the sea during the latest 
geological period, and bounded to the west by a great mountain range mainly clothed 
with an Alpine flora requiring the protection of snow in winter, and to the north by a 
warm temperate region whose flora is mainly of modified subtropical origin — the only 
plants that could occupy the newly-formed region were the comparatively few species, 
which, though developed under very different conditions, were sufficiently tolerant of 
change to adapt themselves to the new environment. The flora is poor, not because the 
land cannot support a richer one, but because the only regions from which a large popu- 
lation could be derived are inhabited by races unfit for emigration. The rapidity with 
which many introduced species have spread in this part of South America is, perhaps, to 
be accounted for less by any special fitness of the immigrant species than by the fact that 
the ground is to a great extent unoccupied. Doubtless, if no such interference had taken 
place, and the operation were left to the slow action of natural causes, a gradual increase 
in the vegetable population would come about. Fresh species of Andean plants would 

* Jour. Linn. Soc, vol. xxi. p. 207. 
VOL. XXXVII. PART I. (NO. 14). ^ 2 K 



Lapageria 
rosea. 

2. Philageria 
Veitchii. 

3. Philesia buxi- 



folia. 



220 DR J. M. MACFARLANE ON THE 

i. Lapageria gradually become modified to suit tlie climate of the plain (perhaps one such recent 



rosea. 



. piniageria instance is supplied in Boopis laciniata of the following list) ; still more slowly new 

Vcitcliii 

.? Phiiesia buxi- varieties would have been developed among the indigenous plants, from which, by natural 
selection, new species would have been formed. No doubt these causes have been in 
action during the short time that has elapsed since Patagonia has existed as part of the 
continent ; but the time has been far too short to allow of the development of a rich and 
varied flora. We are apt. I think, to underrate the extreme slowness of the operation of 
the agencies that modify the forms of vegetation, and the fact that change in arboreal 
vegetation must, other things being the same, proceed much more slowly than with 
herbaceous, especially annual plants. How many of the plants found in fossil miocene 
deposits, enormously more ancient than the commencement of the Patagonian flora, are 
more than slightly modified forms of existing species ? " We may either consider the 
ancestral type to have been nearly related to Phiiesia, and by suitable surroundings to 
have evolved the finer Lapageria; or, conversely, a type allied to the latter may by degrada- 
tion have resulted in Phiiesia ; or some nearly intermediate type, whose home may have 
been on the Andes of South Chili, may have branched off, one on the developmental, one on 
the degradation line. In this intermediate type we should practically recognise our 
hybrid Philageria. It is perfectly within the limits of possibility that on some of the 
Southern Cordilleras of the Andes, about whose flora we know as yet extremely little, a 
natural product may be encountered in which we have very nearly reproduced the 
artificial form Philageria. I can scarcely doubt that some of our hybrids are artificial 
pictures of what once flourished as the progenitors of our present-day species. 



The descriptions which follow pertain to eight hybrid plants and their parents, and these 
have been selected as typical examples of groups of flowering plants, or as presenting us 
in many cases with interesting features in the relation of hybrid to parent, while most of 
them are well known and easily procurable by any who wish to verify details of structure. 

These are the following, w indicating wild or natural hybrids : — 

1. Diantlius Grievei =D. alpinus X D. barbatus. 

2.wGeum intermedium = G. rivale cc G. urbanum. 

3. Ribea Culverwellii = R. Grosmlaria X R. nigrum. 

4.wSaxi/raga Andrewsii =S. Aizoon a S. Geum. 

b.iuEriea Watsoni = E. ciliaris oc E. Tetralix. 

6. Bryantlms erectus = Menziesia empetriformis,va,r. Drummondii. X Rhododendron Chammeystis. 

7. Masdevallia Chelsoni = M. amabilis X M. Veitchiana. 

8. Cyprvpedium Leeanum = C. insigne X C. Spicerianum. 

In addition, about sixty-five hybrids and their parents have been examined in some 
of their parts, and reference will be made at a later stage to evidence of special value 
which some of these yield. 

(b) Diantlius Grievei, x . 

This hybrid was raised by Mr Lindsay of the Royal Botanic Garden, Edinburgh. 
The seed parent is alow-growing, narrow-leaved, one-(rarely two-) flowered pink, attaining 
a height when in blossom of from two to three inches. D. harhatus — the Sweet William — 



MINUTE STRUCTURE OF PLANT HYBRIDS. 



221 



is too common to need description. As every one is aware, many varieties of the latter are 
in cultivation, and the strain which furnished pollen is not definitely known. Equally from 
naked-eye and microscopic examination I regard it as one which had bright green vegetative 
parts, and a corolla white on first opening but gradually becoming crimson with maturity. 
Such a strain existed in the Edinburgh Garden, and flowered during the past summer. 

Accepting this as probable, it may be noted that in D. alpinus the flowering shoot 
produces four to five pairs of vegetative leaves beneath the inflorescence; that of D. barbatus, 
nine to ten; and that of the hybrid, six to seven. The calyx is claret-coloured in the first, 
and one, or it may be all, of the sepals show a red tip. That of D. barbatus is green, while 
the hybrid shows an intermediate tint with red tip to one or all of the sepals. 

I need not describe the naked-eye appearances further than to point out a peculiar 
periodic colouring of the corolla referred to above. When the petals of D. alpinus first 
push out from the calyx their outer surface is white, and the inner is pale pink. On 
full expansion they are rose pink with crimson eye, while before withering they assume a 
deep purple-crimson hue, this happening about nine days after expansion. In the strain of 
D. barbatus noted above, each flower from the bud state till two days after expansion is 
white, then it assumes a gradually increasing pink tinge till the sixth day, when it is rose 
pink, it then deepens till the twelfth day, and before withering is of a crimson colour. In 
the hybrid an intermediate series of changes are passed through, the final colour being 
paler than that of the seed parent. 

Stem Structure. — The mature stems of the second year from which the leaves have 
withered are in proportion of 1 : 1^ or 2 : 3. The stem epidermis of 1 (Plate IV. fig. 7) persists 
as a layer round an outer cortex of 3 to 4 zones of cells, of which the most external are largest : 
within this is a cork cambium, on either side of which six to eight layers of cork and 
phelloderm have formed, the latter adding to the depth of the internal four-zoned cortex 
which surrounds the phloem. In D. barbatus (fig. 9), the epidermis and three to four 
external layers of outer cortex cells easily separate from one to three internal layers, which 
persist and surround a sclerenchyma sheath four to five cell-rows deep, within which a faint 
line of cork cambium can be traced. The internal cortex consists of seven to eight zones, 
whose elements are largest in the middle. In the hybrid (fig. 8) there is a distinct separation 
tendency in the epidermis, and there are one to two cortical cell layers ; internal to these are 
two to three layers lying against a sclerenchyma sheath that is two to three zones deep, 
and the elements of which are half as much thickened as those of the last. The cork 
cambium is evident, and three to four derived layers lie external and internal to it. The 
inner cortex consists of five to six cell-rows whose units are on the average intermediate 
between those of the parent. 

The phloem of the three closely agrees in size of the elements, though it differs greatly 
in total amount in the three forms. 

In 1 the xylem vasa are few in number, but sharply isolated ; in 3 they are numerous, 
and often in groups of two or three ; in the hybrid they are intermediate in number, but 
seldom grouped. 



1. Dianthus 

alpinus. 

2. Dianthus 

Grievei. 
8. Dianthus 
barbatus. 



222 



DR J. M. MACFARLANE ON THE 



/. Dianthus 
alpinus. 

t, Dianthus 
Grievei. 

... Dianthus 
barbatus. 



When the middle part of the aerial flowering stem is examined, i.e. the part towards 
the base of the third internode in 1, of the fifth in #, and of the seventh in 3, the cuticle 
of the epidermis is in proportion of 1^ to 2 J to 3. The outer cortex in 1 is made up of nine 
to ten chlorophyll layers ; in 2 of seven to eight ; in 3 of six. The innermost layer is 
largest in all, but the cells in the three are in the proportion of 5:4: 3. The inner cortex 
is a strengthening sclerenchyma, which in 1 consists of four to five specially thickened 
external bands merging gradually into an inner series of five to six, which become less 
and less thickened. In 3 the two outer layers are greatly thickened, dense, and of small 
size, and abruptly pass into an inner zone, which has thin-walled elements grouped into 
eleven or twelve layers. A condition nearly between these exists in the hybrid. 

When the inner cells are minutely examined under a power of 600", those of 1 show 
extremely little thickening, with at times one pore-canal along a wall side ; in 3 the thicken- 
ing is very pronounced, and three or more pore-canals can be observed along the side ; while 
l 2 has an intermediate amount of thickening and number of pore-canals. The phloem 
does not call for special attention. 

The xylem of 1 consists of a cylinder of spiral tracheae, the number of which in a 
section such as we now describe amounts to 370 ; in % to 720 ; and in 3 to 1260. The 
diameters of the tracheae are in proportion as 3 : 4 or 4 '5 : 6. In longitudinal view the 
stem epidermis of the three shows a considerable abundance of stomata in line with the 
halves of the leaf lamina, but an absence in line with the leaf midrib, and the areas between 
the leaves. On the average, in 1 there are nine under Zeiss' high power with 4 eyepiece ; in 
2 there are seven ; and in 3 there are five. The epidermal cells of the first are 120 ft long, 
slightly wavy in outline, and contain leucoplasts 2 /x, in diameter, which, with the nucleus, 
stain a deep pink hue in eosin solution. Those of 3 are 50 (i long, have straight, 
thickened walls, and the leucoplasts are 4 /a across. In % the cells are about 90 /x long, 
straight or slightly sinuous — not wavy — in outline, and the leucoplasts are in most cases 
about 3 /*. across. It may further be noted that, as the result probably of mechanical 
rather than vital conditions, the cell nucleus in 1 is lenticular, due, I should suppose, to 
elongation by movement in the streaming protoplasm of the long cells. In 3 the nucleus 
is spherical or slightly oval, while that of the hybrid decidedly leans to the first. 

The green subepidermal cortex cells in all have conglomerate crystals. But it may 
here be stated that I have found crystals to be the most unsatisfactory and unreliable of 
any cell content. In these, however, a rather striking and very constant condition can 
be traced. In 1 they are few but large, each being 50 jjl across ; in 3 they are very abund- 
ant but only 30 /a across ; in the hybrid they are more abundant than in 1, less . so than 
in 3, while their size is 35 to 38 jjl. 

The outer cortex is an interesting study, but I shall only compare the two external 
layers of it. In 1 the cells are twice to three times as long as deep, are columnar in 
shape, and have on the average a length of 80 //., while a few small intercellular spaces 
occur between the common walls. The chloroplasts are 3 //, across, and, though rather 
more abundant in the two layers now described, are pretty uniformly distributed through- 



MINUTE STRUCTURE OF PLANT HYBRIDS. 



223 



out all the cells of the cortex. In 3 the cells are nearly all shorter than deep, their 
length is 15 to 25 /x, and they are irregularly rounded in outline ; between them many 
irregular intercellular spaces occur. The chloroplasts measure 5 /x, and are densely 
aggregated in the outer zone, giving to it a dark green aspect. In 2 the cells are distinctly 
elongated, and measure 40 to 45 ti in length ; irregular intercellular spaces are pretty fre- 
quent, and a marked massing of chloroplasts takes place in the outer zone, while each 
chloroplast measures about 4 /x. The parents therefore differ, not only in the size, shape, 
and relation of these cells, but in the amount of elaborative work which they perform, 
while the hybrid progeny blends these peculiarities. 

A reverse case is presented by the inner cortex, for in / the elements are one-third 
the size of those in 3. 

The elements of phloem and xylem differ greatly in size, the small elements of 1 
contrasting with the large elements of 3, while the hybrid is a mean of the two. But 
even the amount of secondary deposit on the spiral tracheal wall can be readily traced 
to stand in the relation of 7 : 8 : 9 in the three. 

Leaf. — The leaf structure of 3 varies considerably at different levels in the same strain 
or variety, and very greatly in the numerous varieties now cultivated in our gardens. 
The description which follows applies to the variety already selected. I regard the upper 
two-thirds of the leaf as the more typical part, and shall refer to it throughout. The 
average depth of the leaf in the three on transverse section through the midrib is as 
2:8:15; the thickness a little to one side of the midrib is as 360 /x : 400 /x : 440 tt. 

On transverse section the upper epidermal cells in 1 are 35 to 40 xi in depth ; in 2 they 
are 55 to 60 /x ; in 3 they are 70 to 80 /x. The palisade parenchyma in 1 consists of three 
layers of round, columnar cells with small vertical intercellular spaces, and the loose 
parenchyma is divisible into a lower dense and an upper loose zone, the chloroplasts in the 
lower being nearly as abundant as in the palisade layer. But the loose parenchyma 
throughout consists of isodiametric cells with small intercellular spaces. In 3 the palisade 
parenchyma forms two rather loosely united layers, which thin out at times into one, or 
enlarge into three ; the loose parenchyma is uniform throughout, and its cells are elongated 
at right angles to the leaf surface and strung together in " confervoid " fashion with large 
intercellular spaces between. In 2 the palisade parenchyma shows two to three rather 
loosely aggregated cell layers ; the loose parenchyma is distinctly divisible into a lower and 
upper area, the former with greater abundance of chloroplasts, but the cells, though often 
nearly isodiametric, form "confervoid" strings. 

In 1, four to six large conglomerate crystals may be exposed in section; in 2 from 
twenty to twenty-five ; and in 3 from seventy to eighty. 

In Plate IV. figs. 1-6, the surface appearances of the upper and lower epidermis are 
given. These speak for themselves, but the stomatic distribution may be summed up in 
figures. Within a limited area, repeatedly verified from different leaves, seventy-three 
stomata occurred in 1, thirty-eight in 2, and two occurred in 3. The number is reversed, 
however, over the lower epidermis, which gave under a high power at one-quarter from 



1. Dianthus 
alpinus. 

3. Dianthus 
Grievei. 

3. Dianthus 
harbatus. 



224 



DK J. M. MACFARLANE ON THE 



/. Dianthus 
alpinus. 

.'. Dianthus 
Grievei. 

.'. Dianthus 
barbatu6. 



the base ten in 1, thirteen in 8, and sixteen in 3 ; at the leaf middle fourteen in 1, seventeen 
in 2, twenty in 3 ; and near the apex forty-eight in 1, fifty-two in 0, and fifty-five in 3. 

The epidermal leucoplasts figured in Plate IV. figs. 10-12, are as striking in the leaf as 
in the stem, but in the hybrid they vary from 2 5 to 3*5 though inclining to the seed 
parent. 

When leaves are macerated, and examined on surface view, it is seen that in 1 the 
crystals are disposed very irregularly in the leaf, are not specially massed round the 
vascular bundles, are nearly uniform in size, and are large in comparison with the size of 
the leaf. In 2 many occur in the mesophyll, but a decidedly greater aggregation occurs 
round the vascular bundles, which in places may seem almost coated with them ; they 
also vary greatly in size. In 3 the vascular bundles are closely encircled in many places 
by them, but large forms are frequent in the mesophyll. I counted the numbers in several 
corresponding areas of the three, and found 40 in 1, 83 in 2, and 135 in 3. 

Sepals. — The gamosepalous calyx in 1 is obconate, dark purple-red in the upper part 
of the tube, but green beneath the bracts, with broad sepaline teeth. In % it is tubular 
obconate. pale crimson-red shading below into dark green and then into light green, and 
with pointed sepaline teeth. In 3 it is tubular, and rich green above shading into light 
green below, and this again into membranous white, while the sepaline teeth are acuminate- 
ciliate. In 1 the outer calyx surface shows faint irregular ridges ; in 3 the ridges are 
very evident, and there are nine to each sepal ; in 2 the development is intermediate. 

On transverse section 1 shows a series of nearly or quite equal fibro-vascular bundles 
beneath and opposite each sepaline groove, the fibre or stereome part of each being very 
large. In 3, three to four shallow grooves intervene between each pair of deep grooves, and 
bundles of corresponding size lie opposite these. In the hybrid the grooves and bundles 
are slightly nearer to the seed parent in type than exactly intermediate. The mesophyll 
of the sepals agrees in fundamental arrangement with that of the vegetative leaf, as do 
the crystals found in it. 

Petals. — The comparative naked-eye appearances of these are set forth in Plate IV. figs. 
13, a, b, c. A little above the junction of claw with blade in 1 there are long unicellular 
hairs, the longest being 2 mm. ; in 3 the hairs are absent, while in £ the longest is \\ mm. 
I have frequently measured these from different flowers, and the hybrid appears always to 
have a preponderating bias towards the seed parent. Above these hairs every epidermal 
cell is enlarged into a little up-directed papilla, which is smallest in 1, largest and thickest 
in 3, intermediate in 2. 

Stamens. — As compared with the parents, these are short and feeble in the hybrid. 
The anthers are small, and have not a plump look. The good pollen grains of 1 are 10 /x 
across; but as grown in the Edinburgh Garden many are small, shrivelled, and manifestly 
impotent, this being probably due to change of habitat. The plants, however, from which 
these were taken annually produce abundance of good seed, so that sufficient good pollen 
must be formed to fertilise the ovules. The pollen grains of 3 are 14 m in diameter, and 
there is seldom an abortive one amongst them. Those of the hybrid are bad in all 



MINUTE STRUCTURE OF PLANT HYBRIDS. 



225 



examples looked at, since they are 8 to 9 m in diameter, and have each a thick wall 
with shrivelled-looking contents. I regard the pollen, therefore, as being entirely impotent, 
and pollination experiments which have been conducted repeatedly, verify this by their 
negative results. 

Nectary. — There is an extremely neat nectar- secreting arrangement worthy of study. 
The pollen parent (3) — a less specialised form in every way to my mind — shows this in 
its simplest state as a small saucer-shaped receptacular girdle (Plate IV. fig. 14, c) between 
the stamens and pistil. The entire depth of the gland tissue is about 180 m. In the seed 
parent a special contrivance has been devised to protect and economise the nectar, for in it 
the bases of the petals have fused with the receptacle, and this has got deeply excavated 
round the ovary to form a nectar ditch the walls of which are lined by gland tissue 
supplied by a Special set of subjacent bundles. The depth of gland tissue is 400 to 
420 m (fig. 14, a). In the hybrid there is an exactly intermediate state of things, in the 
fusion of the petals, shape and size of the gland, and depth of its tissue (fig. 14, b.) 



1. Geum rivale. 

2. Geum inter- 

medium. 

3. Geum urbanum. 



(c) Geum intermedium, x . 

This hjdmd has been regarded by eminent systematists as a true species. Probable 
reasons for this are its extreme frequency of occurrence, the large number of good pollen 
grains, and the usual production of abundant seed. Many suspected its hybrid nature, 
which has been experimentally verified by Gartner and Bell Salter. To speak only of 
the Edinburgh neighbourhood, it is frequent where both parents are found, and is usually 
mixed with these. Thus, in Colinton Glen, Mr Rutherford Hill has gathered quantities ; 
in Carriber Glen, near Manuel, it is very abundant, and has been carefully watched by me 
on repeated visits ; in the valley of the Esk it also appears frequently ; but by far the 
finest locality was pointed out to me by Mr Hill. The woods along the shore in the Dal- 
meny policies beyond Cramond have large areas covered by it alone, or shared also by one or 
both parents. It is easily distinguished by naked eye from the size of the stipules 
developed by the upper cauline leaves ; by the size, position, and colour of the flowers, 
while — as Godron * and others have pointed out — the hybrid is commonly more luxuriant 
than either parent. 

Diverse in naked-eye appearance though the parents are. I have found more difficulty 
in seizing on minute histological differences than in any other set. Marked changes in 
some parts, however, have been effected, which appear in blended manner in the hybrid.t 

Root. — The mature root in all three exhibits a broad annual cork formation, and a 
very rare feature in plants is the formation in all of intercellular spaces between the cork 
cells. In 1 \ the growth of each annual cork ring proceeds so that the oldest brown layer 



* Mem. Acad. Stanisl., 1865, p. 347. 

t Throughout the description I have assumed Geum rivale to be the seed parent, and G. urbanum the pollen parent; 
To select two plants, however, to protect these, and to raise offspring from reverse crosses for comparison, is most desir- 
able, and our knowledge cannot be exact till this is done. , 

X The growth formation of these requires further study. 



226 DR J. M. MACFARIANE ON THE 

/. Geum rivaie. consists of two to three rings of large decayed brown cells ; the layer inside, which 

-'. Geum inter- ° to J 

medium. i s still persistent, consists of rather smaller but neatly quadrangular cells : that more 

■t. Geumurbanum. r . . . ... 

internal is paler in colour, smaller in its cells, but similar in shape to the last ; the inner- 
most layer consists of small transparent quadrangular cells developing from the cork 
cambium. Mr Percy Nicol has accurately illustrated this in Plate V, fig. la, In 3 (fig. 1 c) 
all the cells of the cork layer are very nearly of the same size, no matter what their age 
may be, and they are 1^ to 2 times as broad as deep on transverse section. In 2 there 
is an evident radial enlargement of the cells as in 1, but the shape of the cells takes 
more after 3, though rows of cells may be nearly quadrangular. 

The cortex is similar in the three, except that its cell walls are slightly collenchymatous 
in 1, very strongly so in 3, and most nearly like the latter in 3. The phloem does not 
call for description. 

The xylem of 1 is made up of three to five radiating spokes, which are at first separated 
from each other by the intervention of broad medullary rays. Earely, owing to a slight for- 
mation of interfascicular cambium, secondary xylem patches appear. Each spoke consists 
of xylem cells, spiral tracheids, and many large pitted vasa,the largest measuring 40 /x, across. 
As secondary growth proceeds, interfascicular xylem is laid down, which narrows the 
medullary rays to one or two lines of cells. This secondary growth is of spindle-shaped cells 
and pitted vasa. The xylem of 3 consists primarily, as in the last, of three to five (commonly 
four) radiating masses which are made up of elements like those of 1 during the first year 
or two, except that the diameter of the largest vas is 24 /*. In time, however (the precise 
period has not yet been ascertained, but from the position of the roots on the rhizome, as 
well as their size, I should judge them to be from five to eight yearsold),a ring of dense pitted 
fibroid tracheids mixed with a few small vasa, is laid down outside the softer and earlier- 
formed xylem. It may fairly be suggested as a hypothesis to explain this striking differ- 
ence in the two species that, since G. rivaie grows in moist, damp, shaded, and often 
sheltered situations, it does not need a special strengthening sheath in its roots to resist 
pulling strains ; while G. urbanum, growing often in the open on dry, exposed, and wind- 
swept ground, requires such a sheath for mechanical resistance. In the hybrid the xylem 
decidedly inclines to 1, though the pitted vasa are from 32 to 36 ft in diameter. The 
very characteristic thickened zone of 3 is at most represented by occasional isolated patches 
of fibroid tracheids, which never, so far as I have seen, attain a great size or fuse into a 
ring. We have here a hybrid tissue taking strongly after one parent, and like that parent 
the hybrid almost always grows in sheltered places. 

Stem. — The rhizome and flowering stem are very variable in parents and hybrid alike, 
and will require more detailed attention than I have yet been able to give. The following, 
however, are broad, constant features in the flowering stem. That of 1 has a scleren- 
chyma sheath of soft open tissue, has tracheids and vasa in size like those of the root, and 
large fibroid tracheids. In 3 the sclerenchyma sheath is composed of strongly 
indurated elements, has small tracheids and vasa like those of the root, along with small 
indurated tracheids. The hybrid while intermediate inclines rather to 3, and this 



MINUTE STRUCTURE OF PLANT HYBRIDS. 



227 



is particularly instructive when we bear in mind that it is tall-growing, and needs 
considerable mechanical support. 

Leaf. — On surface view the upper epidermis in 1 consists of cells which are nearly or 
quite straight walled ; about sixty of them cover an area 300 \i in diameter, and among 
these are seven stomata. Long tapered hairs or short four to five celled glandular hairs, 
spring from some of these, and are pretty uniformly distributed over the lamina, though 
more abundant along the veins. The cells of the lower epidermis show zigzag walls, are 
slightly smaller than those above, about sixty-five cells, besides stomatic cells, being within 
the same area, while both simple and glandular hairs are more abundant particularly along 
the veins. From thirty-five to forty stomata occur in the field of view. In 3 the walls 
of the upper epidermal cells are wavy in outline, and of the same size as in 1, but stomata 
are quite absent. Simple and glandular hairs like those of 1 are less frequent. The 
lower epidermal cells are in size and shape like those of 1, but the hairs are very scanty, 
while eighteen to twenty stomata are included in the field of view. In 2 the upper 
epidermal cells are neatly between those of the parents in shape, and though areas occur 
with few, if any, stomata, adjacent ones may present four to six, giving an average 
therefore of three to three and a half. Hairs develop like those of the parents. When 
the relative number of these is compared, it is found that there are twenty-five simple 
hairs scattered over the field of view of Zeiss' objective A and 2 ocular, and five to six 
in 3. The hybrid presents fifteen to sixteen on the average, though in size they rather 
approach those of 3. As regards the number and distribution of the gland hairs, it may 
be noted that while these are seen on a strong vein of 1 in abundance, they equally 
persist along the fine veins, eleven to twelve being visible under l.p. Zeiss' obj. The 
same applies to the hybrid, except that the gland hairs are less numerous. In 3 they 
are entirely confined to the stronger veins where seven to eight may be counted. The 
cells of the lower epidermis resemble those of the parents, but the stomata in number are 
a mean of the extremes in them. 

In a macerated leaf of 1 under one field of view four to six conglomerate crystals 
were counted ; in that of 3 there were ten to twelve; and in the hybrid seven to eight. 
As already stated, however, I do not place much value on these. 

It need only be mentioned in regard to the sepals that these take up a position in the 
open flower intermediate between the reflexed position of 3 and the upright position of 1. 

Petals. — As illustrated in Plate V. figs. 5 a, b, c, the petals of the hybrid are, on the 
average, very neatly intermediate between those of the parents in shape and size. In 1 
the outer epidermal cells have zigzag walls and deep infoldings of the walls at the angles, 
their contour is irregularly elliptical, and they average 65 //. across. In 3 the cells resemble 
somewhat those of the last, though the infoldings are more pronounced but thinner, 
their contour is rectangular, and width 45 ju,. In 1 the inner epidermal cells are greatly 
elongate at the base of the petal, straight walled, and 70 fi long, but upwards they 
become broader and shorter till they are 45 ju, long, and have sinuous walls with knob- 
The cuticle is elevated into ridges, giving a finely striate aspect to the 

VOL. XXXVII. PART I. (NO. 14). 2 L 



1. Geum rivale. 
g. Geum inter- 
medium. 
3. Geumurbanum. 



like infoldings 



228 DR J. M. MACFARLANE ON THE 

/. Geum nvaie. surface. In 3 the elongated basal cells are 26 a. lone;, but they become shorter upwards, 

;.'. Geum inter- « ~ °' » x 

medium. ^^}} they are 15 ju, by 12 a. Their walls are sharply zigzag with fine infol dings. In the 

X Geumurbanum. J r J r r^oo^ ^ o 

hybrid all of these features are intermediate, while the cuticular strise of one parent just 
described are more finely reproduced in the hybrid. 

Stamens. — The outer anther coat of 1 consists of cells of very irregular outline. 
The walls form knob-like infoldings, while the cuticle is raised into prominent wavy ridges 
so strongly developed as almost to obscure the cell outlines beneath. In 3 the cells are 
roughly quadrangular, and their walls have only minute infoldings at the angles. By 
careful focussing one can detect a very delicate ridging of the cuticle. In all of these 
points the hybrid is as exactly intermediate as one can detect. 

The pollen grains of 1 are 26 to 28 a, across ; those of 3 are 18 to 20 a ; and those of the 
hybrid 26 to 28 a. Illustrations of these are given in Plate V. figs. 6 a, b, c. A noteworthy 
feature is the very large percentage of good, sound-looking grains produced by the hybrid. 
The percentage, in blossoms examined from various localities, has fallen as low as 45 to 50 
percent., but in the majority of cases it averages from 85 to 95 per cent., which is as high 
as one usually finds in either parent. 

Pistil. — From the opening of the flower onwards the pistil is an interesting study, but 
I shall only draw attention to the figures on Plate V. figs. 2, 3, 4, which illustrate well their 
external characters. An explanation of the peculiar relationship of the style to the style- 
arm must be possible, but it has not occurred to me yet, nor can I get any account of it. 
That the style-arm must be functional at the time of pollination, or between then and full 
ripening of the fruit, appears almost certain since each falls off previous to fruit dis- 
semination. The formation of a projecting knob on the style-arm of 1, of a similar knob 
on the style-tip of 3, and of one reduced in size on both style-tip and style-arm of the 
hybrid is interesting, but their use is still a puzzle. 

The embryos differ in their shape as do the outlines of their fruit walls. In the 
cells of the three embryos proteids and oil are the reserve materials. In 1 the 
amount of oil is relatively small ; in 3 it is extremely abundant, and exudes from the 
cells as large refractive globules. In # the amount is considerably less than in 3, but more 
abundant than in 1. 

The number of achenes that mature their seeds is very great, and this agrees with the 
high quality of the pollen. The Rev. C. Wolley Dod, however, has stated that with him 
G. intermedium rarely seeds, though other hybrids of Geum do. But the bulk of evidence 
goes to show that the hybrid has a favourable combination of circumstances for its perpetua- 
tion. Growing in shady places frequented by insects, it attains there a high stature, com- 
bining the strong rank growth of 1 with the elongated branching inflorescence of 3. It 
begins to blossom at a time exactly intermediate between the parents, and therefore has 
a great advantage over 3, which has often to struggle with tall-growing summer weeds 
that rush up later than does the hybrid. The half-erect position of the flowers, with open 
spreading sepals and large yellowish-red petals, give it a decided advantage over either 
parent. It is not at all surprising, therefore, that it is so abundant, and, as at Cramond, 



MINUTE STRUCTURE OF PLANT HYBRIDS. 



229 



is fully able to dispute with both parents for occupation of territory. If species evolution 
from forms of hybrid origin does occur, this is one of the most likely to illustrate it. 

(d) Ribes Culverwellii, x . 

This remarkable cross of two very distinct species, the gooseberry and black currant, 
was effected by Mr Culverwell of Thorpe Perrow, Yorkshire. He forwarded specimens 
to Dr Masters, who duly described them in the Gardeners' Chronicle* and then kindly 
forwarded me the material. This proved so instructive that I applied to Mr Culverwell 
for further supplies, and he has furnished these at different seasons of the year. He 
distinguishes two or three varieties, which differ from each other in leaf form, time of 
defoliation, and habit. I selected for examination that which appeared to be most nearly 
intermediate between the parents, but the others which inclined to the black currant 
parent will be treated of at another time. 

Stem. — On transverse section of a stem of 1 in Spring of the second year's growth 
(Plate V. fig. 7), the epidermal cells are rather broader than deep, of a whitish colour, 
and covered by a thick cuticle. 

The outer part of the cortex consists of cells which are small, densely packed, and 
colloid just beneath the epidermis ; but by degrees they become larger, looser, and assume a 
brown colour internally till in the seventh to ninth layers they break down into large 
irregular reticulations loosely attached to the outer cork. The cork, already showing a 
second year's growth, varies greatly in amount according to the size and vigour of the 
shoot. The specimen figured was from a small shoot, and had produced four to five zones 
of cells each year. This explains the apparent anomaly of the hybrid in having eight to 
ten corresponding zones. The old cork cells are 3 to 3^ times as broad as deep. The 
inner cortex (phelloderm) is a relatively narrow band of tissue seven to eight zones 
deep, and made up of elements differing greatly in size. 

Sections of 3 (fig. 9) show epidermal cells that are deeper than wide, of a brown 
colour, and which have a thin cuticular layer. 

The outer part of the cortex consists of a mass of loose, shrivelled-looking brown cells 
that are considerably flattened. The cork of each year's growth is made up of cells that 
are 1^ to 2 times as broad as deep. The inner cortex is a deep band of tissue made up of 
fifteen to sixteen cell layers. 

Sections of 2 (fig. 9) show an intermediate state, not only in the size and shape of the 
cells, but also in colour distribution to the epidermis and inner cortex region. 

The phloem in 1 is in depth as 7 to 10 in 2 and 13 to 14 in 3. The sieve tubes in 1 are 
rather sparse, 1 2 ft across, and are embedded among companion cells with thick refractive 
walls. In 3 the sieve tubes are abundant, 20 to 21 fx across, and are surrounded by a 
moderate number of companion cells with thin walls. In £ the sieve tubes are pretty 
abundant, and the companion cells have slight thickening in their walls. Though the 

* Gardeners' Chronicle, vol. xix., n.s. 1883, p. 635. 



1. Ribes Grossu- 
laria. 

g. Ribes Culver- 
wellii. 

3. Ribes nigrum. 



230 



DR J. M. MACFARLANE ON THE 



/. Ribes Grossu- 

laria. 
8, Ribes Culver- 

wellii. 
.;. Ribes nigrum. 



amount and constituents of the protoxylem are of interest, I may pass to the tracheids 
and pitted vasa after drawing attention to the figures. The secondary xylem of the first 
year is mainly built up of tracheids that are strongly indurated and mostly quadrangular 
in outline ; the vasa are scant, and 18 to 20 /* across. That of 3 has tracheids that are 
moderately thickened, and show a large cell cavity, each is 2\ to 3 times as broad as 
deep ; the vasa are very numerous, giving an open porous appearance to the wood, and 
they are 25 to 28 [i across. The elements of # are very evenly intermediate. 

The amount of pith relatively is as 3 in 1 to 5 in 2 and 6 to 6^ in 3. The pith-cells 
in 1 are circular in outline, the majority of them store starch, and they develop consider- 
able secondary thickening. The pith of 3 appears loose, not only from the large size of the 
intercellular spaces, but because many large cells are devoid of starch contents. All of 
them are polygonal in outline, and the amount of secondary thickening is small. 
While the condition is an intermediate one in %, there is a decided leaning toward the 
latter. The starch grains of the three are very variable in size, but in 1 the largest are 7 fi 
and the average 4 m. In 3 the largest are 3 and the average 1^ m. In 2 the largest are 
5 and the average 3 /a. 

Leaf-Stalk. — In 1 the margins of each leaf-base show short, club-shaped gland hairs, 
which higher up become elongated, and some of these may have secondary hair processes 
branching out from them. In 3 there may be three to eight of the branched hairs, but 
devoid of the club-shaped glandular top ; also an abundance of slender, simple hairs. But 
specially noteworthy are sessile, multicellular, button-shaped gland hairs of a greenish 
colour, which are also abundant over the lamina, and secrete the characteristic scent of the 
black currant. In 2 the short basal hairs and elongated club-shaped upper hairs are both 
present ; the latter at times resembling the currant parent, in being without terminal knob 
though provided with lateral branch hairs. Dispersed over the surface also are greenish 
gland hairs, reproduced from the currant parent, though about half the size. The size and 
shape of the leaf -stalk epidermal cells in 2 are exactly intermediate between those of the 
parents, and the same applies to the base and upper part of the petiole when these are 
examined in section. 

Leaf. — The lower leaf- epidermis of 1 (Plate V. fig. 11) shows irregular cells, with wavy 
walls, that are tolerably thickened, and from some of these arise strong thick-walled, simple 
hairs. Over a given area an average of twenty-seven stomata was recorded. In 3 (fig. 13) 
the cells are straight or flexuous in their walls, which are very thin, and the size of each cell 
averages half the size of one in the former. While delicate hairs are plentiful along the 
veins, they are absent over the areas between, which, however, show many large greenish 
gland hairs. An average of forty-two stomata occurs over a like area as in the last. 
Here, as in the leaf-stalk, the hybrid reproduces the diffuse hairs of the first parent and 
gland hairs of the last, though reduced by half according to careful measurement. 

In the leaf-bundle of 1 the external bundle elements are filled with a dense brown- 
yellow substance, which is absent in the other parent, but comes up in the hybrid as a 
pale yellowish pigment. 



MINUTE STRUCTURE OF PLANT HYBRIDS. 



231 



Petals. — The external surface of the petals in 1 shows relatively large, straight - 
walled, or slightly sinuous cells; the surface of 3 shows small cells with zigzag walls, though 
towards the base they become nearly straight- walled ; in 2 the cells are nearer the latter 
in shape, but nearer the former in size, though it is extremely hard to determine with 
accuracy how far these may not be intermediate. Long delicate hairs grow out from the 
epidermis in 1, none occur in 8, while a few are encountered in the hybrid. The inner 
surfaces resemble the outer except that all the cells are prolonged into tubercular 
outgrowths. 

Stamens. — The pollen cells (Plate V. figs. 10, a, b, c) in both parents are, as a rule, 
extremely good, but those of 3 exhibit considerable diversity in size. This I regard as a 
matter of extreme importance in the discussion of sexual potency, and some attention will 
be given to it later on. The pollen cells of 1 are 27 fi across, and those of 3, 32 /*, while 
those of the hybrid are very bad, consisting largely of small, irregular, shrivelled cells con- 
taining little protoplasm. Here and there, however, one encounters a normal-looking cell, 
filled with finely granular protoplasm as in the parents, and one of these is illustrated in 
fig. 10 b. Another figured beside it would probably prove inferior in pollinating action. 

Pistil. — Muller has pointed out that R. nigrum is almost habitually self-pollinated, 
that R. Grossularia is not only greatly frequented by appropriate insects, but that 
arrangements in the flower itself favour cross pollination. There are one or two pretty 
contrivances which favour the latter view. 

In 1 the style is deeply split to a point, from which downwards a dense coating of long 
hairs grow out so arranged that they form an insect guard to prevent ingress of small insect 
thieves. In 3 the style is simple, and ends in a bifid stigmatic knob ; its surface also is 
glabrous. The style of the hybrid is split to half the extent, and the style hairs are, as 
nearly as one can estimate, half in size and number those of the first parent. 

The receptacular surface above the ovary in 1 has each cell elevated into a fine papil- 
lary hair, and these aid the style hairs in excluding small insects. The corresponding pro- 
cesses in 3 are very minute papillae, which one inclines to regard as functionless, though 
caution is needed in assuming even this. The hybrid has papillae of half the 
length. 

The ovarian surface of 1 is rather sparsely covered with long narrow hairs mixed with 
club-shaped hairs ; that of 3 is densely covered by fine, short, curved hairs, with here and 
there a sessile gland hair ; that of 2 exhibits all the four types just noticed. 

Large loose cells filled with brown contents are found in the mesophyll of the ovarian 
wall in 1 ; the corresponding cells of 3 are all small, nearly uniform in size, and quite so 
in colour ; in the hybrid numbers of the brown cells derived from the former parent are 
readily traced. 

As with other hybrids, I have not yet attempted to examine the ovules minutely, but 
while working at other parts opportunities for observing these occurred, and they seemed 
to be well grown and to contain an egg-cell. Against perpetuation of the plant, however, 
as a pure hybrid is to be reckoned the bad quality of the pollen, while Mr Culverwell, 



1. Ribes Grossu- 

laria. 

2. Ribes Culver- 

■wellii. 

3. Ribes nigrum. 



I 



232 



DR J. M. MACFARLANE ON THE 



/. Saxifraga 

Geum. 
?. Saxifraga 

Andrewsii. 
I. Saxifraga 

Aizoon. 



informs me that he has failed to find fruit on it. The form, however, is one which yields 
valuable results from the standpoint of hybrid histology. 

(e) Saxifraga Andrewsii, x . 

This plant has given rise to some discussion, having been regarded by certain botanists 
as a true species, though by most as a hybrid. It was first brought under the notice of 
botanists and cultivators by the late Mr Andrews, who asserted that he had gathered it in 
a wild state at the head of Glen Carragh, Co. Kerry. Most botanical experts to whom 
the plant was submitted viewed it as a hybrid between S. Aizoon and S. Geum, or some 
nearly related species, and that it had probably originated in Mr Andrews' garden, and 
was confounded by him with some finds from Kerry. It is on this ground well suited as a 
plant to test the accuracy of the present inquiry. My earlier examination soon convinced 
me of its hybrid nature, as well as its relation to S. Geum on the one hand, and a 
crusted species on the other ; but on the " Aizoon " side I had to work very carefully 
over, and compare with each other such nearly related species as S. nitida, S. mutata, 
S. Hostii, &c. Several of these are probably rightly regarded as sub-species or varieties 
of S. Aizoon, though I found them constantly to differ in several fine structural details. 
S. Aizoon entirely satisfied the histological requirements of the other parent, and we 
shall now see how the hybrid blends the features of both. 

Stem. — The structure of this is considerably complicated by the leaf traces which are 
constantly passing out to the crowded leaves, and also by similar root traces. I may, 
therefore, begin with the pith tissue, which is large in amount in 1, and surrounded by a 
ring of bundles. The pith-cells are pretty uniform and large, 50 to 60 /x in diameter, 
and starch granules are abundantly stored up in them. These granules vary greatly in 
size, but the largest are 6 to 7 /u, across. In 3 the pith has a triarch or tetrarch outline 
from its relation to the surrounding bundles ; it is small in amount, its cells are of very 
varying size, the largest being 35 \i across. The largest starch granules are 2 /x across. 
The hybrid rather approaches to S. Geum in having the pith and pith-cells large, though 
not equal to the parent, while the largest starch granules are 4 fi across. Outside the 
pith is a colloid layer traversed by canals, and this is largely developed in S. Geum, 
narrow in S. Aizoon, and intermediate in the hybrid. 

Leaf. — The colour and shape of the hybrid leaf are between those of the parents. A 
special difference in S. Aizoon and all the crusted Saxifrages, as compared with S. Geum 
and its section, is in the excretion from the former of lime salts by the water stomata 
situated at the tips of the serrations on the upper leaf surface. These salts on precipita- 
tion form a crust-like mass over each stomatic area, and give a variegated appearance to 
the leaf. In the " Geum " section salts never precipitate. Though the hybrid often gives 
little indication of a lime crust when grown in one position, or under one set of condi- 
tions, I have repeatedly got specimens in which it was very pronounced to the eye, and 
gave characteristic efflorescence when acted on by acids. 






MINUTE STRUCTURE OF PLANT HYBRIDS. 



233 



The bundle distribution to the water stomata is well illustrated in Plate VI. figs. 1-3, 
and is as follows : — In 1 two lateral bundles run up the leaf-stalk on either side of the 
median bundle, and terminate in the one to two lowest pairs of water stomata, though at 
times a slender branch passes up which partly supplies the third. In 2 the first to the 
seventh pairs in an average-sized leaf are wholly, and the eighth to the ninth pairs 
partly, supplied by the lateral veins. In 3 the first to the thirteenth are thus supplied. 

The upper epidermis of 1 on surface view consists of large, straight, and uniformly 
thick- walled cells, the walls being traversed by pore canals at pretty wide distances. 
There are twenty to twenty-two cells in field of view under Zeiss' D with 4 ocular. No 
transpiration stomata exist above, but towards the top of each serration one to two water 
stomata (Plate VI. fig. 4) are set on the surface of a slight mamilla of epithem tissue. 
In 3 the upper epidermal cells vary in size, some which surround stomatic clusters being 
rather smaller than those of 1, others which lie between the stomata being greatly smaller. 
They all show close-set pore canals, with knob"-like thickening of the walls between these. 
There are fifty to sixty, exclusive of stomatic cells, in the field of view. Though Engler, 
in his Monograph on Saxifrages (p. 13), says — " Die Spaltoffnungen treten sowohl auf der 
Oberseite als auf der Unterseite der Blatter bei alien Arten auf, in der Kegel auf der 
Unterseite zahlreicher," they are entirely absent on the upper surface in the "Geum" 
section, though present on both surfaces in all the crusted Saxifrages already studied. 
They are disposed in little island groups of from three to twelve, each group surrounded by 
small epidermal cells. Surrounding the whole are the large cells already referred to, whose 
contents are less dense than those just described. Each serration in 3 has one to two 
water stomata set in a pocket-like depression of the epidermis, which may rise over them 
in flap-like fashion on one side (fig. 6). Further, in all leaves of true S. Aizoon, a few of 
the surrounding epidermal cells swell out into clear button-shaped knobs. In 2 the 
epidermal cells are nearly the size of those in 1, twenty to twenty-five occurring under the 
field of view ; but this is to be expected, if we bear in mind the relative size of cell and 
leaf in each parent. The thickening of the walls is very evenly intermediate. 

Though a few of the earlier and smaller leaves of an annual rosette have no stomata, 
they can readily be distinguished in most with a hand lens, running up> on either side of 
the midrib. I have not counted the actual number on any leaf, but though there are 
several hundred they are not nearly so abundant as in the " Aizoon " parent, while their 
disposition in islands and their relation to surrounding cells are the same as in it. The 
water stomata are very slightly sunk, or set on a flat surface, and a wave-like ridge of 
the epidermis, rather than a pocket, exists on one side. It is specially interesting, how- 
ever, to find that the epidermal knobs of 3 are reproduced, though in reduced degree, both 
as to number and size (fig. 5). The gradually changing shape of the epidermal cells which 
make up the serration tips in the three is a study in hybrid history which will well repay 
careful tracing out, but without elaborate figures a description would be poor. 

The lower epidermis of 1 has two distinct kinds and sizes of cell somewhat as in the 
upper epidermis of 3. Thus, there are large, wavy-walled, clear cells which collectively 



1. Saxifraga 

Geum. 

2. Saxifraga 

Andrewsii. 

3. Saxifraga 

Aizoon. 



234 



DR J. M. MACFARLANE ON THE 



/. Saxifraga 

Geum. 
8, Saxifraga 

Andrewsii. 
;. Saxifraga 

Aizoon. 



form enclosing masses round the island-like stomatic clusters. Further, there are small 
cells with dense contents which connect the stomata in each island. In 3 all the cells 
are nearly uniform, and are straight or faintly sinuous in their walls ; the stomata also are 
pretty uniformly distributed, so that they cannot be said to fall into island masses. In 
2 the isolation is evident, as is also the separation into two kinds of cell, though in shape 
and size they are quite intermediate. The cells along the midrib region are note- 
worthy, for one can readily trace in these how evenly the hybrid is between the parents. 
Equally instructive are the under cells of the serrations. 

On transverse section the leaf of 1 exhibits a thin cuticle above and rather thicker 
one below ; that of 3 has a thick upper and thin lower cuticle ; and in 2 they are equal in 
thickness. In 1 there is one deep columnar and a second shallower and more irregular 
palisade layer, passing into loose parenchyma. In 3 there are four to five closely-packed 
palisade layers, of which the uppermost is deeply columnar ; the lower are more rounded, 
and pass sharply into the loose parenchyma. In # there are three to four layers, of which 
the uppermost is columnar and the others rounded-elongate. The chloroplasts in 1 are 
large, numerous, and give a dense red aspect to the cells when stained by eosin ; in 3 they 
are small and scattered, so that when stained the cells appear pale, with red spots. In 2 
some of the cells incline to the one condition, and some to the other. The spongy 
mesophyll of 1 consists of about seven layers, whose cells are large, loose, and stellate or 
branching in character ; in 3 they are densely packed and rounded, so that the inter- 
cellular spaces are small, while they average one-half to three-fourths the size of the former. 
The size, mode of packing, and contents of the hybrid cells are quite intermediate. 

Flowering Stem. — In large mature stems of 1, near the radical rosette of leaves, the 
cortex cells are seven to eight layers deep, and pass abruptly into a well-formed scleren- 
chyma sheath of six to eight layers. The largest elements of this sheath are 25 fx across, 
and the walls are so thickened in most as to reduce the lumen to one-third its original 
size. The internal matrix tissue consists of large and tolerably uniform cells. In 3 the 
cortex consists of twelve to thirteen cell layers, which also pass abruptly into a scleren- 
chyma sheath though of narrower proportion than in the last, since the elements are 
smaller, though the layers are as numerous. The largest elements are 20 to 22 ll across. 
The amount of secondary thickening in these is much less, the lumen bearing a ratio to 
the original cavity of seven-eighths. The internal matrix tissue is made up of small 
cells externally, and of larger central ones, none of which, however, equal those of i. 
The hybrid in all of these points is intermediate, the thickening of the sclerenchyma cells 
being specially noteworthy. 

The bundle system in 1 consists of eight to ten wedge-shaped strands, whose bases 
are set against the sclerenchyma sheath. The phloem part has a mass of stereome fused 
with, and scarcely distinguishable from, the sheath, the largest stereid being 20 /x across. 
Internal to this is the phloem proper, made up of large sieve tubes — the largest measuring 
about 30 fx across — and companion cells. The xylem tracheids are very uniform in size, 
aggregated as a wedge-like cluster, and are 18 to 20 ju, across. In 3 the bundles are of 



MINUTE STRUCTURE OF PLANT HYBRIDS. 



235 



two sizes ; one set of seven to eight are early differentiated, remain distinct from l. 
the sheath, and are oval in shape. Another set of smaller size, and numbering eight 2. 
to twelve, are intercalated between these, and are nearly wedge-shaped. The first set s. 
show small external stereome patches, whose elements are little thickened, and the 
largest element is 14 /x across. The phloem is a dense patch of sieve tubes and cells 
differing little in size, the largest tube measuring 10 jx across; the xylem is a narrow 
band of spiral tracheids and xylem cells, the largest averaging 15 fx. The intercalated 
bundles consist only of a small patch of phloem and xylem lying against the sheath. In 
2 the bundles number fourteen to sixteen, and exhibit less disparity than do those of 3. 
They are all more or less united with the sheath, though, as in the latter parent, the 
larger ones tend almost to separate, and in such cases a distinct stereome patch is 
developed, the largest elements of which measure 16 to 17 /x across. Curiously enough, 
while the phloem in appearance and size of its constituent elements rather approaches 
to that of 1, the xylem equally leans to that of 3. 

Sepals. — In S. Geum, as in other members of its' section, the sepals are inferior, and 
after expansion of the flower curve backwards, and become adpressed to the flowering stem 
(Plate VI. fig. 8). The apex is rounded, and carries a single water stoma with associated 
epithem tissue that terminates the bundle. In S. Aizoon the sepals are superior, 
and in expansion grow outwards and upwards, so as to make an angle of 25° to 30°, 
with the ideal prolongation upwards of the axis (Plate VI. fig. 10). The apex is acute, 
often terminated by a knobbed hair, and usually three water stomata, one terminal and 
two lateral, are at the ends of the vascular bundle. In S. Andrewsii the sepals are 
recurved, so that they make an angle of 125° to 130° with the ideal axis (Plate VI. 
fig. 9). The apex is obtuse, and there is one water stoma ; very rarely two or three. 
One could scarcely choose a better series of naked-eye objects on which to demonstrate 
the comparative position assumed by parent and hybrid parts than those now referred to. 

On flower-stalk, bracts, and sepals alike there are glandular hairs, which in 1 have a 
delicate stalk of four to five cell rows and a small rounded glandular head ; in 3 the stalks 
are stout, usually short, and consist of seven to eight cell rows, while the heads are fully 
a half larger than those of 1. Both types of hair are reproduced in the hybrid, 
though less abundantly. The upper epidermal cells in 1 are straight- walled, in 3 they 
are wavy, and in the hybrid sinuous. 

Petals. — In 1, which is the least specialised form, the epidermal cells of the upper 
surface are prolonged into slight papillae, in 3 they grow out as hair processes, and in % 
they are intermediate in length. A peculiarity in colour distribution is that the petals 
of 1 are marked with little crimson and yellow spots towards their base, those of 3 have 
only large deep crimson spots, while in the hybrid the crimson spots alone appear, no 
flowers hitherto examined having shown traces of yellow. 

Stamens.— The anthers of 1 are of a pale pink colour, those of 3 are of a greenish- 
yellow colour, and both contain abundance of good pollen. The anthers of 2 are of a 
pale pink-green or pink-yellow colour, but the pollen is bad, the grains being variable in 

VOL. XXXVII. PART I. (NO, 14). 2 M 



Saxifraga 

Geum. 
Saxifraga 

Andrewsii. 
Saxifraga 

Aizoon. 



236 



DR J. M. MACFARLANE ON THE 



1. Sazifraga 

Geuni 
.'. Saxifraga 

Andre wsii. 
3. Saxifraga 

Aizoon. 



size, smaller than in either parent, shrunken and irregular in shape, and with a few- 
isolated food granules in their cavities. As might be expected, therefore, the 
capsules examined were loose and soft to the touch, and contained brown ovules, none of 
which had matured into seeds equal to those of either parent. 

Pistil. — This, like the pistil of Ribes Culverivellii, demonstrates how exactly the 
position of flower parts in relation to the receptacle is an inherited combination from the 
parents, and here also the hybrid gives us transition stages from the perigynous to the 
epigynous insertion. In Plate VI. figs. 8, 9, 10, micro-photographic illustrations are 
given of longitudinal flower sections. Fig. 8, illustrative of 1, shows sepals, petals, and 
stamens all inserted into a slightly saucer-shaped expansion of the receptacle, on the top 
of which the carpels are inserted. The vascular bundles of the flower-stalk split ; some 
of the branches run outwards beneath the floor of the ovary, give off diverticula into the 
carpellary walls, and then by repeated branchings terminate in the perigynously-inserted 
sepals, petals, and stamens. Other branches are continued upwards, to end in the 
placental tissue and ovules. Fig. 10 is that of 3, in which, by upgrowth of the receptacle 
and fusion of the carpels with it, a completely inferior ovary has resulted. Branches 
from the vascular bundles of the flower-stalk run directly upwards, as in the last, to 
supply the placenta and ovules, while the lateral bundles, after curving upwards and 
traversing the receptacular wall, split up to supply the epigynously-placed sepals, petals, 
and stamens, while prolongations pass transversely across the top of the ovary to the 
epigynously-placed nectary. A glance at fig. 9 proves how exactly the hybrid blends 
the characteristics of the two parents in position of parts, shape of the ovarian cavity, 
position and shape of the styles, &c. 

The styles in the mature but still perfect bloom of 1 diverge at an angle of 40°, the 
stigmatic hairs are columnar and 100 m long. The styles of 3 form an angle of 90°, the 
stigmatic hairs are linear or conical, and 60 m long. The styles of 2 form an angle of 
60° to 65°, the stigmatic hairs are linear or slightly columnar, and 85 to 90 fi long. 
Shortly after fall of the petals the styles in all diverge further, so that those of 1 
form an angle of 80° to 90° divergence ; those of 2 } 100° to 110°; those of 3, 120° to 
130°. 

The nectaries in 1 are little patches placed round the base of the ovary, above the 
region of staminal insertion. Each patch shows one to three surface stomata, exactly like 
the water stomata of the leaf, but reduced in size, and seated above a quantity of epithem 
tissue, below which fine vascular endings occur. The patches are isolated from each 
other by a large-celled, thin-walled tissue. In 3 the larger part of the epigynous area 
between the bases of the styles and insertion of the stamens is a nectar girdle, studded 
over its surface with numerous stomata, set among small epidermal cells, and beneath 
these is a dense ring of epithem tissue lying above vascular bundle endings. The nectaries 
in 2 are patches which are nearly fused into a girdle in the deeper tissue layers, but 
are distinctly broken up on the surface by the intervention of larger cells, after the type 
of 1. I have throughout used the term nectary for these, as do Engler and Muller, but 



MINUTE STRUCTURE OF PLANT HYBRIDS. 237 

I cannot as yet say whether they merely excrete a cool, watery juice, or, in addition, some ]■ Er i ca Tetraiix. 
sweet excretion. The morphology of these nectaries, in any case, is highly instructive. *■ Erica ciliaris. 



(f) Erica Watsoni, x . 

This hybrid between E. Tetraiix and E. ciliaris was first found in a wild state by 
Mr H. Watson* at Truro, Cornwall, where both parents occur. Considerable quantities 
of it have been gathered, and from these supplies have been obtained for the Edinburgh 
Botanic Garden. 

Stem. — The structure in the three is very similar throughout, except that the pitted 
vasa in the xylem of 1 are few in number, and 12 to 15 /x across in the largest 
examples ; those of 3 are pretty abundant, and 20 to 22 m across ; in 2 the number 
is intermediate, and the diameter varies from 16 to 20 ,«, the majority inclining 
towards 3. 

Leaf. — On surface view, the upper epidermis shows straight walled, pentagonal, 
or hexagonal cells, which are 30 /* across. Many of these develop long, delicately- 
striated hairs from the upper end of the cell. In 3 the cells are slightly elongated, 
with wavy walls, are 50 to 60 m across, and only towards the leaf apex are a few striated 
hairs encountered. In 2 the cells are sinuous-angular, and nearly isodiametric, 40 
to 45 m across, and hairs are irregularly and sparingly scattered over the lower leaf 
portion, becoming more abundant towards the apex. 

Transverse leaf-sections of 1 give a thickness of 200 to 250 /x ; of 2, 270 to 330 m ; of 
3, 350 to 400 ju,. The revolute leaf margins of 1 leave about one-third of the leaf 
epidermis exposed ; the margins of 3 are slightly turned back, but at least five-sixths of 
the lower epidermis is exposed ; in 2 a full half is exposed. The proportion of palisade 
to loose parenchyma in the three is as 1 : If : If. The vascular bundle of the leaf 
in 1 is strengthened below by a sclerenchyma mass of eighteen to twenty-two elements, 
and above of ten to fourteen ; in 3 the lower mass is absent, but the upper is developed, 
and consists of fourteen to eighteen elements ; in 2 there is a lower mass of from 
nine to thirteen elements, and an upper of from twelve to sixteen. 

Petals. — The corolla of 1 is regular and ovate-urceolate ; that of 2 is very slightly 
irregular, ovate-constricted, and slightly gibbous towards the base ; that of 3 very 
irregular, oval below, contracted above, and with pronounced enlargement of the upper 
part of the corolla. The average colour of 1 is a waxen whitish pink, of 2 crimsoD-pink, 
of 3 a dull purple-crimson. The outer epidermal cells of 1 all grow out into pronounced 
surface papillae, in 2 the papillse merge gradually into the basal part of the cells, in 3 the 
free cell-surfaces are only slightly elevated. 

Stamens. — The anthers of 1 develop tails that are 9 to 10 mm. long, and the cells of the 
outer anther wall are papillose, like those of the petals ; the anthers of 3 are devoid of tails, 

* Hooker and Arnott's British Flora, 6th edit. 



238 DR J. M. MACFAELANE ON THE 

/. Menziesia and the cells of the anther wall are produced into long papillae, most of which are con- 
va^ 6 B ' stricted above their point of origin. In 8 the anther tails are 3 to 5 mm. long, and the 

enetnB. 118 cells of the anther wall are beautifully intermediate in length of the papillae. A com- 
^h°ama«htus n parative study of these stamens is highly instructive. 

Pistil. — In 1 the ovary is finely hirsute, and at its base there are pouch-like nectaries, 
joined at their orifices by secreting cells. In 3 the ovary is glabrous, and round its base 
occur deep, isolated pouches, with large apertures. In ^ a few hairs occur over the ovary, 
but greatly less than half as many as those in 1* The nectar pouches are smaller than 
in 3, and, so far as I have observed, they agree with 3 in being isolated. 



(g) Bryanthus erectus, x . 

For several reasons I was induced to undertake the examination of this beautiful form. 
First introduced to the notice of botanists by Mr Cunningham, of Messrs Cunningham 
& Fraser's nurseries, it was handed by him to the late Professor Graham for examina- 
tion, though nothing was said as to its origin. As it differed entirely from any known 
species, Graham, ignorant of its true nature, described it as a new species. The 
hybridiser, at that time a youth, stated positively that he had obtained it by crossing 
Menziesia empetriformis, var. Drummondi, with pollen of Rhododendron Chamcecistus. 
Great doubt has been expressed by competent authorities as to the accuracy of this 
statement, and these doubts may have been strengthened, I believe, by the statement 
having been circulated that Menziesia ccerulea — not empetriformis — was one parent, 
and it has even been asserted that the plant has been found in a truly wild state. 
Careful and continued observation of the three plants, hybrid and parents above given, 
would furnish strong reasons for believing in the hybrid origin of Bryanthus, since the 
stature, habit of growth, leaf form, flower numbers, and colour, as well as its failure in 
my experience to produce any quantity of seed, while both reputed parents do, are all 
in favour of Cunningham's statement. I shall first describe the stem shortly, though 
the foliar parts are of greatest importance. 

Stem. — Selecting young first year's shoots of each, we find on longitudinal view of 3 
that the epidermal cells are very irregular in outline, have secondary wall thickenings 
with rather close-set pore canals, and the free surface exhibits fine ridges as in Lapageria. 
Stomata are abundant, as many as seven to eight being the average under the Zeiss' D, 
and still more abundant are short, curved, thick-walled hairs. Long-stalked glandular 
hairs, each ending in a small terminal knob, occur sparingly. In 1 the cells are elongate 
in outline, the pore canals of the walls are unevenly and often distantly placed, and the 
free surface is quite smooth. Stomata are rarely if ever developed, and only a moderate 
number of curved hairs are distributed over the surface. Glandular hairs, composed of a 

* It is possible that an explanation of this is got in lines of variability which 1 sometimes shows. I have pointed 
out {Trans. Hot. Soc. Edin., 1891) that varieties of the species may be nearly glabrous. 



MINUTE STRUCTURE OF PLANT HYBRIDS. 



239 



short thick stalk and greatly enlarged oval head, are about as frequent as are the long-stalked 
ones on the other parent. Bryanthus is quite intermediate in cell size, shape, wall thicken- 
ing, and pore distribution. Four stomata is the average in an area corresponding to that 
cited above. The curved hairs are reproduced in the hybrid, and glandular hairs, reduced 
in size but similar to those on both parents, are found on adjoining parts of the same tissue. 

On transverse section the cortex in the three shows an outer and inner cellular layer, 
with sclerenchyma ring separating them. In 1 the sclerenchyma elements are thick- 
walled and small,, the largest being 12 //, across ; in 3 the elements are slightly thickened, 
but measure 18 to 20 /x ; in 2 the moderately thickened elements are 15 to 16 [x across. 
The tissues of phloem and xylem closely agree in all, except that the pitted vasa of 3 are 
in cross section and relative number half those of 1, while the hybrid is a mean between 
them. 

The amount of pith tissue is as 5 : 4 : 3. The pith is made up of large clear cells, and 
of others which are starch storers, with slightly-thickened pore-marked walls. The latter 
predominate in 3, and they form a reticulate mass which surrounds the longer rounded 
cells. In 1 the former type predominates, the clear cells enclosing patches of starch- 
storing cells. In 2 both types are very uniformly distributed, though at times there is 
a morphological bias towards 3. 

Longitudinal sections of the stem add little to the above, except as to pith tissue. 
The starch-storing cells of 3 are equilateral, or, more commonly, slightly broader than 
long ; each is on the average 20 /x, and a large amount of starch is stored. The starch 
grains are 4 ju across at their largest, though most are from 2 to 3 /x. The clear cells 
are 70 to 80 /jl long, and never store crystals. In 1 the starch-storing cells may be 
quadrangular, but on the average they are 1^ times broader than long, and a small 
amount relatively of starch is stored. The largest starch granules are 6 m across, and in 
all cases they are larger than in 3. The clear cells are 150 to 200 m long, and occasion- 
ally contains conglomerate crystals, 16m across. In 2 the starch-storing cells may incline 
towards one parent or the other in size, though the amount of starch stored and the size 
of the granules fall rather towards 3. The same is true of the clear cells, but a marked 
peculiarity, observed, however, by me in two other hybrids, is that the power of con- 
glomerate crystal formation is not only inherited from the male parent, but appears on 
a more exaggerated scale, there being at least 50 per cent, more crystals in a given area 
of the hybrid pith than in that of the parent. This may point to a greater formation of 
waste products in the hybrid, but better and wider evidence must be forthcoming before 
a final conclusion can be reached. 

Leaf. — In the three the upper epidermal cells are wavy in outline ; in 3 they are twice 
the size of those in 1, and intermediate in the hybrid. On the lower epidermis the cells, 
though smaller throughout, are in the ratio of 9 : 7 : 5. In 3, thirty to thirty-three stomata 
are visible under Zeiss' D with 4 eyepiece. In 1 there are seventy to seventy-five, and in 2, 
fifty to fifty-five. In 3, hairs are entirely absent from the under epidermis. In 1, recurved 
hairs like those of the stem grow out abundantly from the lower epidermis, interspersed 



1. Menziesia 

empetriformis, 
var. 

2. Bryanthus 

erectus. 

3. Rhododendron 

Chamsecistus. 



240 DR J. M. MACFARLANE ON THE 

i. Menziesja \;\t\\ glandular hairs composed of a delicate stalk and large globular head, while in 2 the 

enipetritornus, © x ° ° 

J ar - glandular hairs are wanting, but the curved hairs are present, though shorter and about 

t. Bryanthns ° ° r o 

erectus. one-third as abundant as on the first. Along the line of leaf revolution in 3 there are 

3. Rhododendron ° 

chamrecistus. elongated compound pointed hairs, exactly resembling others which are marginal in position 
and terminate the leaf serrations, except that a few of the latter may terminate in a small 
knob. In 1 the line of leaf revolution develops shortly-stalked greenish gland hairs. In 
2 there are short glandular hairs similar in position and appearance to those in 3, though 
slightly longer in the stalk, and the latter peculiarity, I take it, is derived from 3. The 
compound marginal hairs of 3 are absent. We have here, therefore, the curious condition 
on the lower epidermis of gland hairs belonging to one parent, and marginal hairs 
belonging to another, being alike undeveloped in the crossed offspring. 

Transverse leaf sections are very striking in their relative outlines and depth of 
tissue. 

Flower Parts. — A series of measurements were made of the flower-stalks, and other 
parts in the three, and the average results are given below. In 3 the length of the 
flower-stalk is f to § in. ; in 2, |- to 1 in. ; and in 1 it is 1^ in. The number of flowers in 
a cluster are 2 to 3 in 3, 4 to 7 in 2, and 8 to 14 in 1. 

Sepals. — These in 3 are short, broadly ovate, red or rarely red-green in colour, and 
overlap each other considerably at their bases. In 2 they are ovate-acuminate, overlap 
less than in the last, and are greenish-red, while in 1 they are lanceolate-acuminate, 
scarcely touch at the base when expanded, and are reddish-green in colour. 

The average size of the epidermal cells in the sepals of the hybrid are very exactly 
intermediate, though at times they may vary over small areas. The structure and 
distribution of hairs is again worthy of special note. In 3 each sepal shows externally 
over its base simple curved hairs, with slightly warted surface markings, and over the 
general surface a few glandular hairs whose stalk is long and made up of cells which are 
unevenly placed and taper into each other by oblique ends, while the terminal knob is 
elliptic in shape. In 1 each sepal shows a very few simple hairs at its apex only; 
glandular hairs, whose stalk- cells are short and arranged in transverse rows, and whose 
apex is oval or nearly spherical in outline, occur sparingly over the outer surface. The 
hybrid (2) possesses a few simple though shorter hairs round the apex of the sepal, 
as in 1, while both types of glandular hair occur promiscuously, though in no case 
abundantly. 

On transverse section the sepal of 3 shows an extremely fine cuticular ridging, that of 
1 has it much more developed, while the most careful measurement gives an intermediate 
amount in the hybrid. The mesophyll of 3 consists of three thinning out into two 
layers of chlorophyll cells, that of 1 shows four, while the hybrid shows three which 
become rather small and irregularly packed at their edges. 

Corolla. — The corolla of 3 is salver-shaped, the petals are deeply divided, and each is 
slightly coucave internally. The colour is pale pink below, shading into a more delicate 
hue above. The corolla of 2 is tubular below, becoming slightly salver- or cup-shaped 






MINUTE STRUCTURE OF PLANT HYBRIDS. 



241 



above, and exhibits slight transverse foldings, particularly on first opening of the flowers. 
The teeth of the corolla are flat or very slightly recurved, while the colour is a very 
delicate rose-pink, so that the plant has become a great favourite in gardens. The 
corolla of 1 is tubular, slightly urceolate, transversely plicate round the contracted throat, 
and has strong recurved teeth. The colour is a bright purple-pink. 

Microscopically the outer surfaces of the three are almost alike, but distinct differences 
are observable internally. The epidermal cells of 3 are glabrous over their base and 
upper parts, but about one-third up a zone of long, beautiful hairs grow out, which 
correspond in position with similar ones on the bases of the filaments, and are evidently 
formed as nectar covers. The cells of the base are greatly elongated, five to six times as 
long as broad, but upwards they gradually widen, assume an irregular aspect, and have 
wall infoldings. The epidermal cells of 1 are glabrous throughout, those at the base 
about three times as long as wide, but higher up they widen out, have a sinuous outline, 
and infoldings of the walls. In 2 the cells throughout are intermediate between those of 
the parents, and, further, the hairs of 3 are prettily reproduced, of smaller size, reduced 
number, and in the exact position. 

Stamens. — These are on the average T 7 F to ^ in. long, of a brown -black colour, 
and the filaments have a dense circlet of long fine hairs like those on the corolla in 3. 
In 2 they are ^ in. long, the anthers are of a black-red colour, and a circlet of hairs like 
those of the last, though reduced in number and size, covers the bases of the filaments. In 
1 the stamens are T \ in. long, the anthers are of a deep red colour, and the filaments 
have a very few short hairs at their bases. The pollen grains of 3 are 40 fi across, of 1 
they are 30 /a, and in both cases mature well. Those of 2 are 30 fx, at most, but they are 
almost entirely bad, not more than one in twenty appearing as if capable of effecting 
fertilisation. 

Pistil. — The pistil of 3 is at first short, but eventually, by continued elongation of 
the style, it becomes T 9 ^ in. long, and is straight throughout. That of 1 is T ^ in. long, 
the upper part of the style is curiously curved in knee-like fashion, first downwards and 
then upwards. That of 2 is j\ in. long, and in most cases on first opening of the flower, 
or during the whole blossoming period, is obliquely bent upwards, and then becomes 
straight. The ovary of 3 is richly covered with long gland hairs like those of the sepals 
and sparingly also with simple hairs ; the stigma is deeply five-cleft and 200 jjl across. In 1 
the grooves between the carpels have short-stalked gland hairs, and a few short simple 
hairs; the stigma is entire, slightly depressed in the middle, and 150 /x across. In 2 the 
ovarian surface shows the two types of gland hair derived from the parents, along with a 
few simple hairs; the stigma is deeply depressed or almost lobed, and measures 170 [x 
across. 

The above description of Bryanthus erectus, and of its reputed parents, proves that 
equally in naked-eye and histological characters the parents differ considerably from each 
other, and that the hybrid inherits unblended peculiarities of both in hair appendages, 
and general blending to an intermediate extent in the cells of the organism as a whole. 



1. Menziesia 

empetriformis, 
var. 

2. Bryanthus 

erectus. 

3. Rhododendron 

Chant Eecistus. 



242 



DR J. M. MACEAELANE ON THE 



/. Masdevallia 
amabilis. 

.' Masdevallia 
Chelsoni. 

; Masdevallia 
Veitchiana. 



We thus have overwhelming evidence in favour of the hybrid nature of Bryanthus, and 
a true index of its parentage. As already stated, the report very early gained currency 
that Menziesia ccerulea — not empetriformis — was one parent, and this statement has been 
perpetuated in standard works on the subject. The hybridiser clearly stated and has 
reasserted to me that M. empetriformis, var. Drummondi, was that used by him. What 
evidence, then, it may be asked, can be adduced in favour of the latter over the former ? 
As Mr Lindsay has well pointed out, the hybrid has a growth-vigour which would 
scarcely be expected from union of the dwarf Rhododendron Chamcecistus with the 
equally low-growing M. ccerulea, even if we allow for that luxuriance which hybrids 
occasionally show. But additional evidence is needed, and this, I think, is furnished by 
the calyx and corolla. The external surface of the calyx of M. ccerulea is densely 
studded with glandular hairs, which are scarce in M. empetriformis. The corolla is 
ovate-urceolate in the former, and has a coating of gland hairs over its outer surface. 
The corolla of the latter is tubular, constricted above, and has transverse plications ; its 
outer surface is also quite glabrous. At least two considerations militate in favour of the 
variety "Drummondi" having been used. These are the colour of the flower, which has 
given to the hybrid its clear delicate pink hue ; also the time of flowering, for 
records of the yearly flowering periods at the Royal Botanic Garden place M. empetri- 
formis earliest, Rhododendron a few days later, and Bryanthus later still. But the 
variety Drummondi was this year later in flowering by sixteen days than the ordinary 
species. This, however, would accord well with the flowering period of the hybrid and 
of the other parent. Our evidence, therefore, is wholly favourable to the accuracy of 
Mr Cunningham's statement. 

I would further venture to assert, with considerable confidence, that when a cross is 
effected between Rhododendron and Menziesia ccerulea the progeny will be low-growing 
plants, with dull pink flowers ; that the calyx externally will be more glandular than in 
Bryanthus, that the corolla will be tubular and non-plicate, and that a considerable 
number of glandular hairs will be found over its outer surface. 



(h) Masdevallia Chelsoni, x . 

This hybrid was raised by Mr Seden, a well-known hybridiser on Mr Veitch's staff. 
It was described in the Gardeners' Chronicle for 1880 (pp. 501, 554). M. amabilis, 
the seed parent, is figured and described in Bonplandia and Illustrations Horticole, 
and occurs wild in Northern South America. The pollen parent is found on the Cor- 
dilleras of Peru, was first discovered by Pearce, flowered by Messrs Veitch, and figured 
by Sir Joseph Hooker in the Botanical Magazine, No. 5739. 

I regard the parents as closely related species, on account of their naked-eye appearance 
and microscopic structure. We shall see, however, that there are several important points 
of difference, especially in histological details. Like other Masdevallias, they have a tufted 
habit, form a dense mass of roots whose upper parts are green, have short cylindric 



MINUTE STRUCTURE OF PLANT HYBRIDS. 



243 



stems, slightly, if at all, thicker than the leaf base, which rise above the root tufts. Each 
is really a small pseudo-bulb, as has been correctly represented in the drawing of the 
Botanical Magazine cited above. Miss Woolward is therefore wrong in attempting to 
criticise the drawing adversely and to deny the existence of such a growth.* Both 
parents exhibit, in the size and colouring of the flower parts, considerable variability, as 
was demonstrated by specimens kindly sent me from Glasnevin Gardens, from Mr 
Veitch of Chelsea,, and Mr Buchanan of Oswald Koad. It is not surprising, therefore, 
that the published figures and descriptions do not all agree with each other. The 
microscopic details which give rise to these macroscopic differences are chiefly variations 
in the number and distribution of coloured hair-cells. 

Root. — On transverse section an external velamen of four layers shows cells in 1 greatly 
widened out tangentially, each being three and a half to four times broader than deep. 
In 3 the cells are one and a half to two times broader, and in 2 they are two and a half to 
three times broader. The cells of the epidermis in 1 have their external and lateral walls 
strongly cuticularised in U-shaped manner, those of 3 are only slightly cuticularised exter- 
nally, while 2 shows an intermediate amount both of lateral and external cuticularisation. 

In 1 the root cortex cells have clear colloid walls, specially thickened at the angles, 
as in typical collenchyma, and small intercellular spaces are enclosed by the thickened 
portions. In 3 the cortex cells are large and loose, with rather large intercellular spaces 
enclosed ; the walls throughout are thin, and even at the angles there is little colloid 
thickening. The cells of 2 are intermediate in size, amount of colloid thickening, and 
development of intercellular spaces. 

In 1 the cells of the bundle sheath and of the xylem are strongly thickened, so that 
the lumen — specially of the xylem elements — is greatly reduced. In 3 these elements 
are of large size and are slightly thickened, while in 2 all the roots that I have yet 
examined approach nearer to 3 than to 1. In 1 the pitted vasa are 18 /a across, in 3 
they are 35 /a, and in 2 they are 28 /u. 

Longitudinal root sections of 1 show cortex cells from the third layer inwards, which 
are greatly elongated and have thick, white, colloid walls. In 3 these are loose, thin- 
walled, slightly irregular in shape, and are, on the average, rather broader than long. 
In 2 the cells are considerably longer than broad, and show a moderate degree of 
colloid thickening. 

Stem. — Only a few details need be referred to here. On transverse and longitudinal 
section of the cortex of 1, the cells are greatly elongated ; their walls are thickened so 
that slit-like deficiencies with pore apertures are left, and between the cells are small 
intercellular spaces. In 3 the cells are slightly longer than broad, many have no 
thickening deposits, but a few show a very pretty secondary spiral thickening. Many 
of the cells surround large intercellular spaces. In 2 the shape and size of cells, as also 
the size of the intercellular spaces, are not only intermediate, but spiral cells like those 
of 3, though with less thickening deposit, are distributed among the unthickened ones. 

* " The genus Masdevallia." 
VOL. XXXVII. PART I. (NO. 14). 2 N 



1. Masdevallia 

amabilis. 

2. Masdevallia 

Chelsoni. 

3. Masdevallia 

Veitchiana. 



244 



DK J. M. MACFARLANE ON THE 



.'. Masdevallia 
amabilis. 

g. Masdevallia 
Chelsoni. 

.'(. Masdevallia 
Veitchiana. 



The elements of the bundle sheath, the sieve tubes and pitted vasa, all conform in the 
hybrid to what one might expect. 

Leaf. — Each leaf is divisible into a terminal laminar portion and basal persistent 
petiole. Between the pseudo-bulb and petiole, also between the petiole and lamina, 
layers of cork cells develop, which first cause shedding of the lamina, and at a much later 
period of the petiole. 

The epidermal cells of 1 are variable in size, rounded in outline, and have thick, 
white, refractive walls ; the cells of 3 are elongated and have thin walls ; the hybrid 
shows a condition between the extremes. The number of stomata over the leaf area are 
as 8 : 12 : 18, but they vary in number in any leaf over given parts of it, being sparse 
towards the base and apex, abundant over the middle two-thirds. A careful comparison, 
therefore, of the whole area requires to be made to obtain this result. 

The mesophyll tissue that surrounds the bundles alike of petiole and lamina in 1 consists 
parti}' of quadrangular cells, whose thickened walls show slit-like deficiencies with pore 
apertures. One can readily trace that the slits follow an oblique, almost spiral course 
round the wall, but the thickened areas between are too broad to give even the semblance 
of a spiral marking to it (Plate VII. fig. 1). In 3 the mesophyll throughout, but specially 
that towards the base of the lamina, is crowded with oval or quadrangular cells, larger 
by half than the slit cells of the last, while the walls exhibit beautiful spiral thickening 
(Plate VII. fig. 2). The secondary spiral thickening bands are of considerable thickness, 
as one can learn from sections. The hybrid shows fewer spiral cells ; in truth, towards 
the leaf apex they become very rare, and the spiral deposit is less in amount, but these 
peculiarities demonstrate the moulding action of the other parent. From careful com- 
parison of the parent and hybrid cells, I incline to view the spiral cell as a modification 
of the slit-marked or pitted one through great elongation in oblique or spiral direction 
of the slits. Examples can be got in the hybrid where greatly elongated and oblique 
slits alternate with thickened bands. 

Apart from the question of hybrid production, it is worthy of note that the 
parents could be easily distinguished from each other histologically by the presence or 
absence of spiral cells in the leaf tissue, though the leaves are strikingly alike to the 
naked eye. 

Perianth Segments. — The three sepals which form the most attractive part of the 
flower are of a uniform purple-red tint in 1 ; in 3 the inferior halves of the two lower 
sepals are of a yellow-red colour, flushed with purple, while the upper halves and superior 
sepal are either bright red or may have a faint purple flush ; the hybrid has a pretty 
wide distribution of the purple flush over the inferior sepals and the ground colour is 
more subdued than in the last, but richer than in the first. This colour distribution is 
proved on microscopic examination to be due to bladder-like hairs filled with a purple 
cell-sap. These spring from the epidermal tissue, the cells of which contain yellow 
chromoplasts. In 1 the epidermal cells are irregularly rounded in outline, and they, 
as well as subjacent cells, have a small number of minute pale yellow chromoplasts, 



MINUTE STRUCTURE OF PLANT HYBRIDS. 



245 



each averaging 1^ to 2 /x across. The hair cells are very numerous, uniformly distributed, 
variable in size, and of conical shape, with rounded apex (Plate VII. fig. 3). In 3 the 
epidermal cells are as a rule elongated and sharply angular, their chromoplasts are very 
abundant, of a bright yellow colour, and partly distributed through the peripheral proto- 
plasmic layer, partly aggregated in many cases round the nucleus. The presence of these 
gives the yellowish-red colour to those areas of the sepals from which hairs are absent. 
The hairs are globular or broadly obovate in shape, and though they vary a little in size, 
the degree of variability is not nearly so pronounced as in 1 (Plate VII. fig. 5). In 2 the 
number, size, and tint of the chromoplasts, as also the shape and size of the cells which 
contain them, is a very fair mean between those of the parents, while the pigment hairs 
are of extreme interest as showing that the variability in size inherited from one parent 
is reproduced, though on a less exaggerated scale, in the hybrid progeny (Plate VII, fig. 4). 
Occasionally in the hybrid, as in M. Veitchiana, compound hairs, formed of a short 
columnar stalk and enlarged head, are observed. 

Stamens. — The cells of the anther sacs in 1 are small and rounded ; of 3 they are 
elongated and angular ; and of 2 rounded-angular. The pollen grains of 2 are quite 
equal in quality to either parent, so far as microscopic examination can decide. If, 
therefore, the ovules are correspondingly good, this hybrid should be capable of per- 
petuation. 

The suggestions already made as to the evolutionary origin of Lapageria and 
Philesia might equally be urged here. Both parents are inhabitants of the mountains 
of South America, and their close histological affinity leads one to look for some common 
ancestral form. We are now acquainted with several species that are nearly related, and 
which frequent the same regions, and it is possible that a comparative study of their 
tissues might aid us in determining the lines of development on which these have 
advanced, and the possible relation of the artificially produced hybrid to some type which 
once existed or still exists. 



1 Cypripedium 
Spicerianum. 

2. Cypripedium 

Leeanum. 

3, Cypripedium 

insigne. 



(i) Cypripedium Leeanum, x . 

This hybrid orchid was raised in Messrs Veitch's Chelsea Garden Nurseries by cross- 
ing of C Spicerianum with pollen of C. insigne. It is a very evenly-balanced cross on 
first appearance, but, as we shall show, some parts of it exhibit a pronounced one-sided- 
ness of development. 

Root. — I have carefully examined roots of the three, but find them fundamentally 
alike, so far as my supply of material has enabled me to make an exact age 
comparison. 

Leaves. — Comparative surface views of the upper and lower epidermis show con- 
siderable differences in the number of epidermal cells and of stomata over a given area. 
The following results illustrate this. In C. Spicerianum the lower half of the upper 
epidermis showed, under Zeiss' D with 4 eyepiece, five to six cells, over the upper half 



240 



DR J. M. MACFARLANE ON THE 



/ Cypripediiun 
Spiceriamun. 

','. Cypripedium 
Leeanum. 

3. Cypripedium 
insigne. 



six to seven and a half cells. In C. Leeanum the lower half showed eleven to fourteen, 
the upper half ten to twelve. In C. insigne the lower half showed fifteen to seventeen, 
over the upper half thirteen to fifteen. This gives an average of 6^ : 12 : 15. 

In C. Spicerianum the lower epidermal cells and the stomata were distributed as 
follows : — 



Base, . 


5 stomata and 21 




epidermal cells 


Between base and middle, 


4-5 


23 




>> )> 


Middle, . 


6-7 


27 




M J> 


Above middle, . 


6 


25 




>r j> 


Near apex, 


7 


25 




» >> 


Apex, 


. 6-7 


25- 


■26 


)> » 



In C. Leeanum as follows : — 



Base, 


5-6 stomata and 27 




epidermal cells. 


Between base and middle, 


6 


30 




>> >? 


Middle, . 


7 


32 




» » 


Above middle, . 


8 


35 




)» » 


Near apex, 


8-9 


37 




)> >> 


Apex, 


9 


38- 


•40 


» » 



In C. insigne as follows : — 

Base, 

Between base and middle, 

Middle, . 

Above middle, . 

Near apex, 

Apex, 



7 stomata and 40-43 epidermal cells. 

8 „ 45 

9 „ 45-48 
9 „ 45-46 

10 „ 45-46 
10 „ 45-48 



Thus the average number of stomata in the first is five, and of epidermal cells 
twenty -four to twenty -four and a half ; in the second, of stomata seven to seven and a 
quarter, and of epidermal cells thirty-three ; in the third, of stomata eight and three- 
quarters, and of epidermal cells forty-five. 

On transverse section at one-fourth length from the leaf apex the upper 
epidermis in C. Spicerianum shows deep columnar cells, varying from 440// to 460 m 
in depth, and continued from midrib region to about the middle of each laminar 
half; they then become shallower, passiug from 350m to 240m, and near the margin 
are reduced to 60 m in depth. In C. Leeanum those on either side of the 
midrib are 400 m to 430 m in depth, they then fall to 350-380 m, again to 280 m, 
then to 200-220 m, and near the margin they are 60 m in depth. In C. insigne 
those on either side of the midrib are 380-400 m in depth, they then fall to 
360-380 m, then to 320-350 m, then to 280-300 m at the middle of each laminar 
half; they then decrease rather suddenly to 140-160 m, then to 100-120 m, and near tbe 
margin they are 60 m in depth. If the variability in the hybrid about the middle of 
tbe inner half of the lamina be constant, it might indicate an unstable and wavering 



MINUTE STRUCTURE OF PLANT HYBRIDS. 



247 



tendency towards one or other parent. The relative depths of leaf sections and of the 
spongy parenchyma in these may merely be referred to as conforming in general effect 
with what we have given above. 

Flowering Stem. — The surface appearance of most of the epidermal cells agrees in the 
three. In C. Spicerianum a few four-celled hairs are found just beneath the flower 
bract, otherwise the stem is glabrous. In C. insigne rounded cells are present over 
the whole length of the stem, and from these five- or six-celled pointed hairs spring. 
Glandular hairs are about equally abundant. Each is made up of a stalk of four cells, 
and a terminal club-shaped part of three cells. In the hybrid both kinds are present, 
but more sparingly and of smaller size than in the latter parent. 

In C. Spicerianum five to six layers of rounded and neatly arranged cells with 
thickened walls lie beneath the epidermis. They surround small sharply defined and 
nearly triangular intercellular spaces. In C. insigne there are ten to twelve la}' - ers of 
larger and looser cells than in the last, the walls of which are feebly thickened. They 
surround irregular and rather large intercellular spaces. In the hybrid there are eight 
to nine layers with moderately thickened walls, and the intercellular spaces are between 
those of the parents in size and form. The sclerenchyma sheath is alike in the three. 

In the bundle system the spiral tracheids are 18/* in the one parent, 30 m in the 
other, and 25 m in the hybrid. 

Sepals. — The large superior (in position) sepal is a specially instructive study from 
the standpoint of hair formation. That of C. Spicerianum has the halves strongly re- 
flexed so as in many cases nearly to meet behind ; it is of a dull stone-white colour 
except along the midrib, where is a slight amount of purple-red pigment. That of 
C. insigne is flat or slightly arched inwards, of a pure white colour at the sides, but 
the middle area is varied by numerous large purple-black spots distributed over a 
greenish -white background. The hybrid exhibits a slight reflexion of the halves, has 
the white lateral parts of each parent, and the spots of the latter, but these are lighter 
in tint and usually smaller in size. 

Except where otherwise mentioned, the size and outline of the cells agree in the three. 
In C. Spicerianum the margin is fringed by many glandular hairs like those described 
above, but very few are found over the outer surface, where simple multicellular hairs 
are most abundant. In C. insigne simple hairs of five to six cells not only fringe the 
margin, but are copiously distributed over the outer surface, along with a few glandular 
hairs. In the hybrid simple and glandular hairs are equally abundant round the 
margin, and the first also occur over the exterior along with a few of the latter. The 
inner sepal surface of C. Spicerianum is copiously and uniformly beset with gland- 
tipped hairs, which in all cases spring from colourless cells of the epidermis, but have 
some or all of their cells often filled with a rich ruby pigment, the presence of which in 
the hairs gives the dull stone colour to the sepal. In C. insigne there is a rather scant 
distribution of simple hairs, except over the dark purple spots which are quite glabrous. 
In the hybrid a few simple hairs are inherited from the latter parent, but there is an 



1. Cypripedium 

Spicerianum. 

2. Cypripedium 

Leeanum. 

3. Cypripedium 

insigne. 



248 DR J. M. MACFARLANE ON THE 

' C Sprcerian™ m abidance of gland-tipped ones derived from the first parent. They are, however, less 
-'• Cypnpedium abundant, for over equal areas under Zeiss' A objective, there were sixteen to eighteen 

Leeanum. ~ J ' & 

5. cypripedium m Q Spicevianum as compared with nine to eleven in the hybrid. The spotted areas 

insigne. ± L •> r 

in the hybrid are quite glabrous, as in the other parent. This mode of hair distribution, 
alike as to position and relation to epidermal colour distribution, is all the more remark- 
able when we remember that the gland hairs of C. Spicevianum and the hybrid spring 
from colourless cells, but are nevertheless filled, in at least the three to four lowest, 
with a pigment like that filling the epidermal cells, which form the areas that are invari- 
ably glabrous in C. insigne and in the hybrid. Further, while along the dark purple 
line that traverses the middle of the sepal in C. Spicevianum, both types of hair of a 
ruby colour spring from similarly coloured cells, and while the middle of the sepal in C. 
insigne is glabrous and colourless, the purple line is reproduced in the hybrid though in 
a rather diffused state, and both kinds of hair spring from ruby cells of it. 

The median inferior (in position) sepal shows in C. Spicevianum a moderate number 
of simple multicellular hairs externally, and great wealth of glandular hairs internally. 
C. insigne shows the converse condition, viz., abundant glandular hairs externally, and 
fewer simple hairs internally, though the relative numbers are more nearly equal than in 
the former. In the hybrid there is a pretty uniform distribution of both types alike 
on the outer and inner sides. 

Petals. — The lateral petals are mainly of interest from their hair distribution, but 
they may be passed over as they do not share the striking peculiarities of the sepals. 
The outer surface of the labellum has wavy-walled cells, which, for shape, size, &c, are 
quite alike, though the colour contents vary. Internally they agree, except in colour and 
hair distribution. C. Spicevianum has hairs spread uniformly along the bottom of the 
slipper ; C. insigne shows two types, one simple and multicellular, the other short and 
club-shaped, being composed of three small stalk cells, and a terminal knob cell. In the 
hybrid both kinds of hair are encountered though reduced in size and number. 

Stamens. — We may neglect the abortive stamens except the crescentic one which 
represents the third of the outer whorl, and which merits detailed study. In C. 
Spicevianum, both outer (anterior) and inner (posterior) surfaces of it are quite smooth, 
and only a very few hairs exist towards the top. It measures from 3 m. at its thinnest 
to 6*5 m. at its thickest part. In C. insigne, the outer surface is covered by yellowish 
glassy warts, which appear under the low power of the microscope as magnificent greenish 
yellow papillae, each ending in a hair. The inner surface is also hair-covered over its 
upper region. The microscopic resemblances of the hybrid seem all to be towards the 
latter parent till sections are made and examined, when the size of the papillae and of the 
cells forming them, as also the hair distribution, are found to be a reduction by half of 
the conditions of the latter parent. 

The pollen of C. Spicevianum is slightly smaller than that of C. insigne, and is pale 
yellow, while in the latter it is greenish yellow, and in the hybrid dull yellow. The 
pollen of the hybrid has a round but rather granular and hard look. 



MINUTE STRUCTURE OF PLANT HYBRIDS. 249 

Gynostemium. — I need only refer here to the position of the bundles and their 
relation to the stigmatic lobes. In C. Spieerianum the three stigmatic bundles run 
so that lines joining the corners of the stigmatic lobes would pass through their middle ; 
in C. insigne the bundles would be considerably outside these lines, while in the hybrid the 
inner margins of the bundles would be touched, or they would lie just without the bundles. 

The stigmatic lobes of C. Spieerianum are equal in size and deep depressions separate 
them ; in C. insigne two of the lobes are short and one is long (one-half longer than 
the other two), and except between the short lobes the depressions are shallow ; in C. 
Leeanum one lobe is rather larger than the other two, and the depressions are inter- 
mediate in character between those of the parents. 

Pistil. — The ovary of C. Spieerianum is glabrous ; that of C. insigne is densely 
covered with a short belt of glandular and pointed hairs, which show great diversity in 
size. In the hybrid the latter description suffices, except that the hairs are reduced in 
number by about one half. 

(k) Some General Observations on Hybrids. 

Instead of recording all that has been observed regarding the histology of other 
hybrids, I shall now select some special features which seem to deserve consideration. 

Stomatic Distribution in Hedychium Sadlerianum and its Parents. — The number of 
stomata over a given area has^ been found in most eases to be intermediate in a hybrid 
between that of its parents. But on overhauling the hybrid named above, I was greatly 
puzzled to account for apparent discrepancies in relative distribution, and at first ascribed 
these to the choosing of leaves that did not exactly correspond in time of development. 
After exercising every care, however, in this and other respects, the results were 
discouraging. It should her& be stated that the upper epidermis of H. Gardnerianum 
has few stomata, and is glaucous owing to a rather thick wax layer covering the cells ; 
the upper epidermis of H. eoronarium is bright green, devoid of wax covering, and pro- 
duces a few rather long hairs. The stomata of the latter are ten to twelve times more 
abundant than those of the former. The upper epidermis of H. Gardnerianum gave an 
average over equal areas of two stomata ; that of H. eoronarium, thirty-two ; that of the 
hybrid, twelve. Over the lower epidermis the numbers, as taken from a large series of 
observations made over the entire leaf surface of several leaves, were 10 : 20 : 22. That 
this exceptional result was not to be explained in the same way that we, in a later part of 
this paper, attempt to explain the tendency which a hybrid often has to sway towards 
one or other parent seemed evident, particularly since other parts of the hybrid are very 
exactly between those of the parent. 

It appears possible that we may have here a morphological adaptation in the hybrid 
for physiological work, or, in the truest sense, a case of physiological selection. We are 
dealing with two parents, one of which develops a thick wax covering to a thick and 
somewhat leathery epidermis, the other a thin cuticle and scant hair growth from a com- 



250 DR J. M. MACFARLANE ON THE 

paratively delicate epidermis. Is it possible, one may ask, to obtain an equally balanced 
morphological and physiological blending of such leaf peculiarities ? In other words, were 
the hybrid exactly intermediate morphologically, would it be able to carry on efficiently 
its physiological work ? To be in a position to answer this we would require — what is 
still a desideratum — accurate statistics as to (a) the amount of transpiration from 
stomata on the upper as compared with those on the under leaf surface ; (b) the effect on 
elaboration and transpiration activity of a wax covering ; (c) the relation to transpiration 
of leaf thickness, specially in the chlorophyll layers. On all of these points we are still 
largely ignorant ; but everywhere in Nature we see form suiting itself to function to a 
degree that often effects remarkable alteration in structure, and we may therefore suggest 
hypothetically that the apparently anomalous details of the above hybrid may receive a 
true interpretation on the line indicated. 

Starches of Hedychium Species and of their Hybrids. — In two cases already 
described it has been stated that appreciable differences exist in the starch granules of 
parents and hybrids, those of the latter being between those of the parents. But as 
these were very small and variable in size, the discovery of forms in which size was com- 
bined with tolerable uniformity was very welcome. Such were obtained from a series of 
Hedychium hybrids, one of which has already been named. 

H. Gardnerianum, the one parent of H. Sadlerianum, forms strong rhizomes, whose 
storing cells are large, but scantily filled with starch in all that I have examined. Each 
starch grain is a small flat triangular plate, measuring 10 to 12 m from hilum to base 
(Plate VII. fig. 13), and the lamination is not very distinct. H. coronarium, the other 
parent, forms smaller and fewer rhizomes, and the starch-storing cells are from half to 
three-fourths the size of the last, but these are densely filled, particularly in the central 
parenchyma, with large starch granules. Each is ovate, or in some cases is tapered 
rather finely to a point at the hilum. They are from 32 to 60 ^ long, measuring as 
before, and the lamination is very marked (Plate VII. fig. 15). The cells of the hybrid 
are on the average between those of the parents ; but if one may judge by opacity of cells, 
the amount of stored starch approaches more closely to that of the latter parent. The 
grains may best be described if we suppose a rather reduced one of the first parent to be 
set on the reduced basal half of one of the latter. The lamination also is more pronounced 
than in the first, less so than in the second (fig. 14). 

A second cross was effected by Mr Lindsay with H. coronarium, and examination of 
the rhizome starches proves that the second hybrid approaches very closely to the 
species parent. But the grains of H. Lindsayi illustrate microscopically a phenomenon 
which has been repeatedly referred to, viz., the greater variability and instability of a 
second over a first hybrid, for many of the grains (in some specimens the majority) 
have fantastic shapes, appearing as if undergoing rapid disintegration by leucoplasts, or 
perhaps more truly as if the latter were incapable of building up the shells of starch in 
a regular and uniform manner. 

A set of crosses has been effected between H. elatum and H. coronarium. The 



MINUTE STRUCTURE OF PLANT HYBRIDS. 251 

grains of the first (fig. 16) are like those of H. Gardnerianum, except that they are larger 
(18 to 24 /x), and that the lamination is coarse. The grains of the hybrid are larger than 
those of H. Sadlerianum, and exhibit even more evident lamellae (fig. 17). They measure 
on the average 40 m, but vary from 30 to 50 n. 

But not unfrequently all of the above hybrids have mixed up with the more 
typically intermediate ones some which can scarcely, if at all, be distinguished from 
the small grains peculiar to one parent, while very rarely I have observed grains 
that were so large and rounded as to pass for those of H. coronarium. Now, when 
describing the epidermal leucoplasts of Dianthus Grievei (p. 22), it was stated that 
though the average was nearly 3 /*, some measured 2*5 /* or slightly less, others as much 
as 3*5 /«. The occurrence of these, and similar minute differences in protoplasmic masses, 
or in formed materials like starch grains which are due to manufacture by these masses, 
induced me to prepare a set of micro-photographs, and to project lantern transparencies 
of these on a 7-ft. screen. Thus it was possible to study their dimensions more exactly 
than under the microscope. It was then found that while the shape, appearance, and 
size of most starch grains of Hedychium, of Dianthus leucoplasts, of Geum and Mas- 
devallia chromoplasts, were intermediate, examples might be got which reverted power- 
fully to one parent, and, so far as they have yet been studied, the reversion was most 
frequently towards the parent with the more minute cell-contents. 

Hairs of Rhododendron Species. 

In the hybrids that have been fully described one or two cases presented themselves 
of parent plants being provided with hairs different from each other in structure, and one 
only or both of these being inherited by the hybrid. This did not involve a pronounced, 
if at all discernible, leaning of the hybrid to either parent in naked-eye appearance. 
Many striking illustrations of this nature are afforded by species of Rhododendron, which 
further furnish remarkable verifications in the epidermal papillae of the exactness with 
which microscopic details are handed down from parent to offspring on reduced or enlarged 
scale, according to the interacting effect of the other parent. 

Many of the Himalayan Bhododendxons, including such well-known species as R. 
ciliatum, glaucum, formosum, Dalhousiw, Veitchiana, &c, have on their under leaf 
epidermis brown, brown -red, reddish-green, or green scale hairs, with intramural glands, 
the structure and development of which have been traced by De Bary.* But most of them 
further show a fine leaden- white tint, due to the outgrowth of epidermal papillae from many 
or all of the cells. Others again, such as R. Edgeworthii, have in addition long twisted 
unicellular hairs, which soon after their first formation get filled with air, and their walls 
assume a brown colour. I will not now deal with the scale hairs further than to say 
that in size, colour, and outline they may vary greatly in two parents, and that those of 
one parent only may be inherited by the hybrid offspring. 

* Comp. Anat. Phan. and Ferns, Eng. ed., 1884, pp. 96-97. 
VOL. XXXVII. PART I. (NO. 14). 2 O 



252 DR J. M. MACFARLANE ON THE 

The epidermal papillae are absent as such in R. ciliatum, but the free surface of each 
epidermal cell is slightly convex (Plate VII. fig. 6) ; and as incident light rays are not 
greatly interfered with, the surface has a dull green aspect. In R. glaucum each epidermal 
cell grows out as a little wart or papilla, measuring 7 fx (fig. 8), and light rays falling on the 
sides of these and on the epidermal surface from which they spring interfere with each 
other, so that a leaden-white colour results. In the hybrid R. Grievei* each epidermal 
papilla is 4 to 5 /a in height (fig. 7), since the convex cell surfaces of the first-named parent 
aid in making each slightly longer than half that of the other parent. 

A cross of R. ciliatum with R. Edgeworthii was effected by Mr Lindsay. The leaves 
of the hybrid have a good deal of the wrinkled character of the latter parent, but are 
entirely destitute of the dense woolly covering to the under epidermis, which is so con- 
spicuous a feature of that parent. Transverse leaf sections of R. Edgeworthii expose 
the scale hairs cut across ; also each epidermal cell grows out into a straight papilla 
slightly constricted in its middle, and measuring 14 to 16 jx in height (fig. 12). Depres- 
sions in the epidermis are occupied by knob-like outgrowths of it, from each of which a long 
twisted hair arises. The hybrid shows, in addition to scale hairs, papillae 9 to 10 [x in 
height, but though there are depressions in the epidermis that appear to correspond to 
those of R. Edgeworthii, the long hairs are never produced. 

The well-known hybrid between R. formosum and R. Dalhousice may now be taken. 
Leaf sections of the former (fig. 9) show short epidermal papillae, which may be straight, 
but mostly are slightly inclined, so as collectively to form a broken circle round each stoma, 
and, therefore, the rudiment of a wind chamber. They measure 12 to 14 /x, in height. 
Leaf sections of R. Dalhousice (fig. 11) present papillae that are 16 to 18 fx in height, and 
are curved inwards in groups round the stomata, so as to form very efficient wind 
chambers. The hybrid exactly blends the extremes of the parents in the size and angle 
of bending of the papillae (fig. 10). 

In the above set of Rhododendron parents and hybrids, therefore, a complete grada- 
tion in size and position of epidermal papillae is established. If an equally gradual 
transition could be traced among existing species, not only in the size and position of 
the papillae, but in other structural minutiae, a key to specific relationship would 
undoubtedly be obtained. 

Colour of Hybrids and of their Parents. 

Reference may now be made to certain features which are better treated of as a 
whole, though isolated references have been made to most of them in the foregoing 
descriptions. First we may deal with hybrid colour distribution, and in doing so we 
must keep in view the surface area over which any pigment is to be distributed, specially 
in the case of dissolved pigments like red and blue, or their combinations. Since these 
depend in most cases on relative acidity (for the red) or alkalinity (for the blue) of the 

* I am greatly indebted to Mr Grieve of Messrs Dickson's nurseries for a liberal supply of this hybrid that 
was raised by him. 



MINUTE STRUCTURE OF PLANT HYBRIDS. 253 

cell sap, slight chemical change may produce marked colour effect. Yellow, on the other 
hand, being a pigment intimately united with and formed in protoplasmic masses, is less 
liable to rapid change. White we naturally consider to be due to refraction of light from 
cell surfaces, from walls which bound intercellular spaces, &c. If, therefore, a cross is 
effected between two parents, one of which has large richly-coloured petals or other parts, 
the other parent smaller and pale-coloured parts, the hybrid may appear to have a greater 
resemblance to the first, though exactly intermediate, for half of the large amount of rich 
pigment from the one parent which will be diffused throughout its cells, will apparently 
give an exceptional richness of effect. A good example of this is furnished by Rhodo- 
dendron Nobleanum, which was raised from the scarlet, rather large-flowered R. arboreum 
and the greenish or pinkish white, smaller-flowered R. Caucasicum. To a casual observer 
the hybrid seems to take wholly after the first. An arrangement of the three blossoms 
side by side effectually demonstrates how nearly the hybrid ranks between the parents. To 
take another illustration from vegetative parts, the fine hybrid Nepenthes Mastersiana is a 
cross of 2V. sanguinea, the pitchers of which when mature are of large size and vary in colour 
from greenish-scarlet to crimson, and of N. Khasiana, which bears long narrow pitchers, 
varying from yellowish -green to dull red-green. The hybrid accordingly presents a 
corresponding latitude in colour effect, though on the average it is greenish-crimson. 

The opposite relation equally holds true, as proved by the dark purplish crimson 
Rhododendron atrovirens, when crossed by R. ciliatum, giving the bright crimson- 
pink R. prcecox, and similarly the small-flowered dull pink R. glaucum, when crossed 
by R. ciliatum, gives the pale pink R. Grievei. 

Though cases have been recorded of peculiar and apparently inexplicable colour blend- 
ing, there are few, I am persuaded, which will not yield to ordinary methods of analysis. 
A very interesting series of crosses and recrosses of East Indian Rhododendrons has been 
studied by Professor George Henslow,* and some of the colour combinations described 
are such as one would scarcely have expected, but it is quite possible that the evolution 
of some new chemical product through hybrid combination may simplify or quite explain 
the apparent anomalies. 

If we are to put any trust in colour statistics as hitherto given, we are bound to con- 
clude that the balance of evidence is in favour of a hybrid inheriting half the amount of 
colour effect from each parent, whether due to union of the same or another colour series. 
Even when colours belong to opposite ends of the spectrum, evenly balanced fusion seems 
to result, though the day is not long past when this was regarded as almost or quite im- 
possible. Thus the brilliant scarlet-flowered Delphinium nudicaule has been crossed in 
the Edinburgh Botanic Garden with the dark blue-flowered D. cashmirianum, the hybrid 
product being of a lurid purple-red hue, which, when set between the parents, is the per- 
fection of blending. Though Gartner failed to cross the blue and red varieties of 
Anagallis, this has since been effected. It is also true that few if any allied species, 
even though very different in colour, resist steady and repeated attempts to cross. 

* Gardeners? Chronicle, vol. ix. p. 618, 1891 ; Trans. Boij. Hort. Soc, 1891. 



254 DR J. M. MACFARLANE ON THE 

But that the crossing of species which have diverse colouring, even though nearly 
related, often produces profound molecular disturbance and instability in the offspring, was 
early recognised by Darwin, and has repeatedly been insisted on since. Thus Darwin 
obtained from a cross of the red and blue Anagallis mongrel progeny, some of which were 
red, some blue, and some intermediate in colour. This may be accounted for by 
supposing that a state of instability had been brought about by an overstraining of 
that characteristic elasticity of the protoplasm, which in most cases of species-crossing 
gives an evenly blended product. 

That there may be morphological peculiarities associated or correlated with colour 
production, and entirely confined to one parent, is clearly shown by the account given of the 
large se}3al of Cypripedium Leeanum. With a copious production of a deep crimson 
pigment in C. insigne, aggregated into large sharply-defined spots, there is an absence 
of the simple hairs that are abundantly present over the rest of the inner sepal surface. 
The other parent has many gland-tipped hairs over the areas, which are uniformly white 
in it, but spotted in C. insigne. Now in C. Leeanum, while the pigment spots are 
undoubtedly much paler in colour, their presence always points to an entire absence of 
hairs. This, along with other facts shortly to be reviewed, points not only to a molecular 
instability in the hybrid tissues, but to an ultimate predominance of one sexual element 
over the other, alike in the formation of chemical products and in the upbuilding of 
permanent tissues. 

We shall see later on that the petals of the remarkable graft hybrid Cytisus Adami 
are usually exactly intermediate in colour between those of the yellow and purple species 
with which they are associated on the same tree, even though many of the tissues take 
entirely after one or other parent in a mixed manner ; but instances appear to be not 
unfrequent * where half or some part of a petal is like one parent, the remainder like the 
other. Here again is one-sided sexual predominance in colour formation. 

The evidence at present to hand warrants the assumj)tion that the majority of plant 
hybrids are exactly intermediate between the parents in colour production if the colours 
readily blend, but that some show a greater or less degree of instability, which passes 
by transition cases to complete resemblance to one parent. 

III. 
Comparative Chemical Constitution of Hybrids and of their Parents. 

This subject might appropriately enough have been dealt with under the last 
head, while my observations are very fragmentary. I give them as they are, in the 
hope that thereby attention may be drawn to what is a wide and important though 
difficult field for research. 

On placing twigs of Cytisus Laburnum, C. purpureus, and the intermediate graft 
hybrid, or C. Adami, in separate bottles of alcohol for preservation, I was surprised soon 

* Dakwin, Animals and Plants, vol. i. p. 414. 



MINUTE STRUCTURE OF PLANT HYBRIDS. 255 

after to notice that while the young stems and leaves of the first had bleached completely, 
those of the second had taken on a deep, dull, brown- grey colour, and those of the third a 
tint inclining to the second, but greatly lighter. The colour suggested the probable presence 
of tannin, and on application of the iron test this was verified. Sections of fresh leaves of 
C. Laburnum gave a faint but undoubted tannin reaction, those of C. purpureus turned 
to black-brown, while the hybrid assumed a hue considerably darker than in C. Laburnum. 
That the hybrid inherits about half the amount of tannin supply, compared with the 
sum-total of the parents, is evidenced if we take into consideration the large leaf surface 
which it forms and through which the tannin has to be diffused. 

As yet only a few seminal hybrids have been noticed, which from their behaviour 
suggest similar results. These are — (a) Geum intermedium and its parents ; G. rivale, 
discolouring to a brown hue, and G. urbanum, to a white or whitish-yellow. (6) 
Saxifraga Andrewsii and its parents, (c) Ribes Culverwellii and its parents ; but none 
of these have been chemically tested. 

Odour of Hybrids and of their Parents. 

This resolves itself also into a chemical inquiry, but practically no attention has been 
given to it hitherto. A few notes may be recorded. The common Sweet William 
(Dianthus barbatus) is strongly and agreeably scented ; D. alpinus has no odour ; D. 
Grievei has an odour like that of the first, but decidedly reduced in strength. 

Rhododendron Edgeworthii is an agreeably and powerfully scented species, with large 
blooms ; R. ciliatum has small blooms, and is scentless or nearly so ; the hybrid has a 
pleasant odour, that entirely agrees with the first physiologically. 

The large white blossoms of Hedychium coronarium give off a powerful and agreeable 
odour, greatly reminding one of that from the butterfly orchid ; the smaller yellow 
flowers of H. Gardnerianum give off a heavy odour, which in the opinion of most is 
not particularly pleasant ; the hybrid gives off an odour which physiologically strikes 
one as quite different from either parent, but unless by chemical analysis one could not 
tell whether it results from commingling of the other two or is an entirely new chemical 
combination. A wide series of observations on this subject is greatly to be desired. 

Flowering Period of Hybrids and of their Parents. 

It is a matter for regret that our information on phenological phenomena is extremely 
meagre. Till within the last ten years the only continuous observations that have been 
made and recorded, so far as I know, are those from the Edinburgh Botanic Garden ; but 
they covered a very limited field, and have only been extended widely within the period 
just named. Professor Hoffman's valuable tables and notes have not helped me, as 
they refer to a limited number of true species only. 

The behaviour of some well-known hybrids and parents led me to watch the flowering 



256 DJt J. M. MACFARLANE ON THE 

periods, and to search available literature on the subject. This was confined to Mr 
Lindsay's record* of 1408 plants flowered on the Rock Garden, to a few others given 
in the same publication over a period of twenty years or more, and largely to unpublished 
lists of plants flowered on the Rock Garden during the last ten years. During two 
seasons also (1890 and 1891) several wild hybrids and parent forms have been watched. 

Naturally, for exact comparison of the flowering period of hybrids and of their parents, 
specimens of the three should be planted in such positions near each other as to ensure 
that all shall have similar conditions of soil, exposure to sun, wind, and rain, drainage, 
&c, if the two parents agree in habitat. But in the case of parents which flourish, as a 
rule, under different environmental surroundings, an imitation of these should be carried 
out as perfectly as possible under cultivation, or, better still, frequently repeated observa- 
tions of the wild plants are to be preferred. As proving the necessity for this, the 
behaviour of Geum intermedium and its parents might be described. G. rivale 
affects watery places and shady moist copses, always attaining best average growth and 
ripening the greatest number of fruit clusters when these requirements are fulfilled. 
G. urbanum grows in " borders of copses, hedgebanks," &c. (Hooker), and thrives best 
in such circumstances. When grown in a damp place, its vegetative luxuriance checks 
its reproductive capacity. But this latter situation, if a sheltered one and well exposed 
to sunlight, hastens its flowering period by a week to a fortnight. For an accurate 
estimation, therefore, parents growing under normal surroundings must be watched, and 
the average date of first opening of a blossom on several plants should be taken, while 
for the hybrid an even wider and more careful record is requisite. 

Geum intermedium. — The first blossoms of G. rivale opened in several places 
visited this year (1891) on 7th to 9th May ; those of G. intermedium on 20th May in the 
open, and on the 26th in shady places ; G. urbanum was gathered on 6th June in an 
exceptionally sheltered spot, but the first flowers opened, in four other localities, from 
12th to 18th June. 

Carduus Carolorum. — The one parent, C. palustris opened its first capitular florets 
in several localities from 20th to 22nd June, C. Carolorum on 25th June, and C. hetero- 
phyllus on 2nd July. 

Erica Watsoni. — E. Tetralix was gathered wild in three places, with first flowers 
opened, on 24th June ; E. Watsoni flowered in the open beds on the 15th July, and on 
the Rock Garden at Edinburgh on the 20th July ; E. ciliaris opened in the beds on 
28th July, and on the Rock Garden on the 14th August. 

During 1887, when the later flowering plants suffered from severe droughts, E. Tetralix 
blossomed on 30th July, E. Watsoni on 1st August, and E. ciliaris on 14th September 
at the Rock Garden, but the first named was gathered that year by us in a wild state on 
the first Saturday of July. 

Rhododendron prcecox. — R. atrovirens opened this year (1891) on 21st January, 
and from an average of twenty years' observations blossoms on 2nd February ; R. prcecox 

* Trans. Bot. Soc. Edin., vol. xvii., 1888. 




MINUTE STRUCTURE OF PLANT HYBRIDS. 257 

was in full bud in two positions, and had just opened in a third when cut by frost on 
1st March ; H. ciliatum opened on 23rd April. 

In 1887 I find that the first flowered on 3rd February, the second on 26th February, 
and the third on 9th April. 

For additional information regarding other hybrid Ehododendrons I would refer to a 
short article in the Gardeners' Chronicle, vol. ix., 3rd ser., p. 753. 

Many of our hothouse orchid crosses promise, if carefully studied, to give excep- 
tionally fine results. Hybrids must in not a few cases have been obtained by pollinating 
an early blossom of an early flowering species with a late blossom of a late flowering 
species, or at least, if this method has not been adopted, different degrees of temperature 
have been employed to check or rush forward the flowering period of the plant. Thus 
Cypripedium Ashbourtonice and C. Harrisianum are examples from a genus. 

Montbretia crocosmcejlora. — During 1890 M. Pottsii opened on 28th July, the 
hybrid on 20th August, and Tritonia aurea in a cool house on 1st September. 

Lilium Poivellii. — Lily hybrids have been rather rare hitherto. The present one was 
reared and flowered by C. S. Powell, Esq. of Old Hall, Southborough, to whom I am 
indebted for a magnificent example. It reached me in full flower at a time when 
L. Hansoni had shed its parts by a week, and fourteen days previous to the opening of 
L. dalmaticum. In reply to a query from me, Mr Powell wrote : — " Your observation of 
the blooming period of the hybrid being intermediate is correct. ' Hansoni ' bloomed 
before any hybrid expanded, and the other parent, ' dalmaticum,' is now in bloom — ten 
days after the others (hybrids) were over." 

While the examples now given show the hybrid to be very evenly between its 
parents, there still are cases which pass to the extremes ; my information, however, 
about these is in every instance imperfect. But it may be observed here that Dianthus 
Lindsayi appears to bloom nearly or quite as early as D. alpinus, while D. barbatus, 
grown from youug plants, opens from a fortnight to three weeks after. The relative 
age of the specimens here may have something to do with the results. Again, Bryanthus 
erectus opens shortly after (one to four days) Rhododendron Chamcecistus, according to 
present statistics, while Menziesia empetriformis, var. Drummondi, opens from fifteen to 
twenty days later. 

We cannot as yet attempt to formulate definite conclusions, for a large accumulation 
of statistics from different localities is needed, but the evidence points strongly, and in 
some cases positively, to the flowering period of hybrids being more or less exactly 
between that of the parents, while some vary to a greater or less degree towards one 
or other parent. 

Constitutional Vigour of Hybrids. 

This subject brings us face to face with a very complex and deep-seated chain of 
phenomena which are the sum-total of the action and reaction of the living protoplasm 
in relation to its surroundings. The complexity of the subject, and difficulty of judging 



258 DR J. M. MACFARLANE ON THE 

how to gauge results accurately, need not deter us from attempting in the future to 
grapple with it. My attention was drawn to it by observing the resisting power of 
Montbretias during the past winter (1890-91). In the note above referred to in the 
Gardeners' Chronicle I shortly drew attention to it, and the sequel will best be understood 
by quotation of the passage : — 

" The behaviour of Montbretia Pottsii, Tritonia aurea, and M. crocosmcejiora in the 
Edinburgh Garden during the past winter seems suggestive. The corms of the first 
appear scarcely to have been injured. Those of the hybrid have been largely killed off, 
at least to the extent of 60 per cent., while Tritonia — never hardy in exposed ground — 
has survived only where it is planted against, and can creep along, the outer side of a hot- 
house wall." 

Confirmatory evidence api3eared, curiously enough, in the same Number. A corre- 
spondent, after a visit to Van Houtte's nurseries at Gend-Brugge, wrote: — "The 
Montbretias, about 6 inches below ground, were mostly frozen ; the most hardy variety, 
Pottsii, was unharmed." Another correspondent wrote : — " Montbretia Pottsii has sur- 
vived, though M. crocosmcejiora has almost if not altogether died out." 

Philesia buxifolia is a hardy plant, and resists well our winter colds. Lapageria 
rosea requires the temperature of a cool hothouse to flourish, while the hybrid succeeds 
if kept protected from frost and the more cutting winds. In the southern counties of 
Britain it lives and flowers out of doors. 

An extremely important line of investigation, alike on theoretical and practical 
grounds, is suggested by these relations to climatic surroundings, and a solution of the 
problems involved can only be successfully attained by utilisation of our botanic gardens, 
and the establishment in these, or in some special institute, of experimental biological 
departments. 

As somewhat akin to the above may be mentioned the growth-forms and growth- 
periods of Carduus Carolorum and its parents. C. palustris is a biennial which forms 
during the first season a short root and stem system with a close-set rosette of leaves. 
In the succeeding season the stem elongates greatly, develops a branched mass of capitula, 
and when these have shed their fruits the whole plant dies away. In C. heterophyllus an 
extensive system of creeping perennating rhizomes is formed which annually send up leaf- 
and flower-stalks. From the axil of a hypogeal scale a bud grows out, or several may arise 
in a season, which run horizontally underground, often to a length of twelve to thirty inches, 
from the flowering shoot. These, as well as the old rhizome portion, persist after the 
aerial stem has died away. In C. Carolorum there is a curious combination of both growth 
forms, with the practical outcome that the plant is perennial like the latter parent, though 
in a weaker and less perfect manner. At the base of many flowering shoots a bud or buds 
arise in the axil of a hypogeal leaf, and these grow outwards and upwards, sometimes 
attaining a length of from three to ten inches. The parent part in most cases dies away, 
but the lateral shoots continue the growth. A very similar state of things is encountered 
in Montbretia crocosmcejiora and its parents. 



MINUTE STRUCTURE OF PLANT HYBRIDS. 259 



IV. Cytisus Adaml 

Before attempting to generalise on the facts gathered from investigation of sexual 
or seed hybrids, we may first examine minutely a plant which has excited universal 
attention and interest since its first production in 1825. I refer to Cytisus Adami, now 
regarded by most as a graft hybrid. Darwin * summed up the generally received ideas 
regarding it, and added additional valuable observations. A list of leading papers on 
the subject is appended, which may guide those who wish to trace the literature of it.t It 
may suffice here to say that M. Adam, a nurseryman near Paris, budded, according to his 
own account, a shield of the small tufted species C. purpureus on the common laburnum 
(C. Laburnum), hoping only thereby to get a stronger and more free-flowering variety 
of the former. The bud seemed for the time to die back, but from the region of its 
insertion a strong shoot developed later, which he considered to be the desired bud sport 
of C. purpureus. As such he sold it, and we may judge of the surprise excited when 
it was found a few years later that this assumed an arborescent habit, and broke out 
into yellow and purple portions similar to branches of the parents, as also into strong 
twigs, bearing flowers exactly intermediate in form and colour. 

Some have attempted to assert that we have to deal here with an ordinary seminal 
hybrid, but not only have we the unvarnished account given by its producer, the striking 
mixture and at the same time sharp distinctness of the three growths which make up the 
composite organism and are simultaneously produced on it, leave little doubt in my 
mind of its graft-hybrid origin. I know of no seminal hybrid which imitates it, though 
one or two approach it, as, for example, Noble's Clematis and Berberis Neuberti.\ I 
wish further to show that the microscopic characters agree with such a conclusion. 

No account of its histology had appeared when I published my preliminary note in 
the Gardeners' Clironicle ; but shortly after Marzell Branza referred § to it in a few 
sentences thus : — 

" Medicago falcata-sativa. — This plant presents in its different parts (trunk, stalk, 
floral axis, petiole), and in all the tissues of its organs a kind of medium between the 
same parts of the two parents. Thus, for example, the stem by the disposition of the 
bark, of the liber, of the wood, of the pith, establishes the transition between the stem of 
Medicago falcata and that of M. sativa. It is the same in the hybrids Cytisus Adami 
and Sorbus hybrida." 

* Animals and Plants under Domestication, 2nd edit., 1890, vol. . pp. 413-417. 

t Annates de la Soc. de I'Hort. de Paris, torn, vii., 1830, p. 93; Loudon's Gard. Mag., vol. vi., 1831, p. 335; viii., 1832, 
pp. 473-474 ; The Phytologist, vol. i. pp. 652, 908 ; Gard. Chron., 1841, pp. 265, 325, 336 ; 1842, p. 397 ; 1857, pp. 382, 
400, 454 ; 1864, p. 244 ; 1865, p. 509 ; 1866, pp. 565, 733 ; 1868, p. 575 ; 1870, pp. 767, 831 ; 1884, pp. 772, 810, 811 ; 
Bratjn, "Rejuvenescence," Ray Soc. Bot. Mem., 1853; Bot. Zeitung, 1873; Focke, Pflanzen-Mischlinge, pp. 519-522; 
Darwin, Animals and Plants under Domestication, 2nd edit., 1890, vol. i., pp. 413-417 ; Morren, E., Belgique Horticole, 
vol. xxi., 1871 ; Caspary, Bullet, du Congres Internal de Botanique, Amsterdam, 1865, p. 72 ; Masters, " Grafting, its 
Consequences and Effects," Popular Science Review, April, 1871 ; Macfarlane, Gard. Chron., July 26, 1890. 

\ Masters, Gard. Chron., " Bud Variations," 1891 ; Focke, Pjlanzen-Mischlinge, p. 21. 

§ Comptes Rendus, August 1890. 

VOL. XXXVII. PART I. (NO. 14). 2 P 



260 DR J. M. MACFARLANE ON THE 

The italics are mine, and my observations, repeatedly and carefully verified on a great 
variety of material, are the opposite of his. 

Alike to acknowledge my indebtedness, and to help any who may wish in future to 
compare the growths for themselves, I would mention the following sources from 
which material has been drawn : — 

From the gardens of Hopetoun House, Mr Smith has kindly furnished repeated 
supplies from three fine specimens growing in the shrubbery of the flower-garden close 
to the brook. Mr Smith has watched the behaviour of these for me, and states that the 
yellow and purple parts blossom nearly simultaneously, or the former has slightly the 
advantage, while the mixed part opens several days later. Both parent branches pro- 
duce abundant fruit, but he has never noticed a pod on the third. 

From Cowden Gardens, Dollar, Mr Nicolson has sent me two fine branches showing 
the three types in bloom ; and similarly I am indebted to Mr Dow, gardener at New- 
byth, Prestonkirk, and to Mr Fortune, Blairadam. The last-named informs me that 
a very fine and large tree was blown down three years ago ; the young plant, 
however, promises well. Dr Scott informs me that two good trees grow in his grounds 
near Melrose, one also is in the garden of Mr Lyall at Newburgh, and another in 
Dr G. Carnachan's garden at Clynder, Eoseneath. 

I have further received specimens of the yellow and intermediate types from Mr 
Chapman, gardener to C. Jenner, Esq.. Duddingstone Lodge, from Mr Hunter, gardener 
at Lauriston Castle, and from Mr Fairgrieve, of Dunkeld Palace Gardens. The trees 
at Duddingstone Lodge have not as yet developed the purple form, if the germs of it 
exist in the plants. The two specimens at Lauriston are specially noteworthy, since Mr 
Smith informs me that he remembers having seen the three growing on adjoining branches. 
The trees appear to have reached or passed their maximum of growth, and the purple 
bunches have entirely disappeared now. Mr Fortune informs me that the purple tufts 
frequently die away on one part of the tree and burst out in fresh regions ; and I have 
noticed a less marked tendency in the intermediate or " Adami " part, so that the purple 
portion is shortest lived, the intermediate longer, and the yellow is the most persistent. 
A tree in the Edinburgh Botanic Garden produced the three so recently as seven 3^ears 
ago, but no traces of the purple and red have appeared during 1890 and 1891. 

The Dunkeld tree is interesting, for the " Adami" flowers on it are completely double, 
which is a rare occurrence among leguminous species. Mr Fairgrieve has watched for 
me the flowering period of the yellow and intermediate parts, and he finds that the first 
precedes the second by five days. 

Beside the above, many other trees appear to be scattered over the country, if we 
may judge from gardening literature. The oldest that I have examined appears to be 
from fifty to sixty years, if we may judge from specimens of the common Laburnum of 
known age and size. 

In the following description, unless expressly stated otherwise, reference to C. Labur- 
num and C. purpureus may apply either to the isolated parents, or to the parts of these 



MINUTE STRUCTURE OF PLANT HYBRIDS. 261 

as found growing on the " Adami " organism, for I have found the yellow and purple 
parts of the composite tree to agree exactly with those of the parents, except that the 
" purpureus " part occasionally shows slight deviations which will afterwards be 
referred to. 

Stem. — When young twigs of the first year from C. Laburnum and C. purpureus, 
or shoots of these as found on the composite tree, are examined with the naked eye, they 
show a smooth green surface, and such is also the case even in four- or five-year-old branches. 
But while the twigs of "Adami" may remain smooth and shining during the first year, 
they almost invariably begin to develop a rough, ruptured, and freckled surface in 
the second year. A simple explanation is got when sections are compared. In C. 
Laburnum a cork is formed beneath the epidermis towards the close of the first year, 
and ere long the epidermis peels off as a delicate film. The cork layer is composed of 
clear, thick-walled refractive cells of a yellowish colour, three to five layers of these being 
formed each year from the phellogen (Plate VIII. fig. 3). No rupture or peeling off of 
these may take place for from thirty to fifty years. In C. purpureus a phellogen is not 
developed till the third or fourth year, and even after that the amount of cork produced 
is very small, so that the stem is quite encircled by the persistent epidermis, since it 
attains to no great size (Plate VIII. fig. 1). The strong shoots of C. Adami inherit to 
a certain degree the vigour of cork formation from C. Laburnum but in a reduced, 
localised, and retarded manner, while the epidermis has a thick cuticle and shows great 
persistence as in C. 'purpureus. We find, therefore, that broad but isolated lines 
or patches of cork develop which eventually rupture the epidermis outside them, and 
give the rough aspect to the shoots, since they have neither the even uniformity of 
formation nor of persistence that the cork of C. Laburnum has. Plate VIII. figs. 2 and 
2 a illustrate stages in the process from a second year's twig, where the irregularity which 
usually characterises the cork development of C. Adami has been well delineated by 
my former student, Mr Percy Nicol, to whom I am indebted for several careful 
drawings. 

In C. purpureus the cortex consists of seven to ten thin-walled cell layers, while 
in the other two it consists of thirteen to fifteen layers, the cell walls of which are colloid 
and refractive. But one feature of the cortex calls for special mention. In C. purpureus 
five longitudinal strands of indurated fibroid elements are imbedded in it at rather 
irregular intervals (fig. ls.s.), These are entirely unrepresented in the other parent 
and in "Adami." 

The phloem stereoid masses are of large size, and pretty uniformly disposed in C. 
Laburnum and C. Adami, but in C. purpureus they vary greatly in size, though they 
are in all cases smaller than in the first two. The amount and size of the elements of 
the phloem proper in the first two agree very closely, the zone being relatively broad, and 
the sieve tubes of large size, as compared with the narrow zone and small sieve tubes of 
the last. 

As regards xylem, when the average of a series of preparations from different 



262 DR J. M. MACFARLANE ON THE 

trees is taken, the amount of wood formed by C. purpureus in the first year is small, 
while that of the second year is nearly twice as deep. As shown by the figures (Plate VIII. 
figs. 2, 3), the opposite is true, of C. Laburnum, and C Adami is tolerably intermediate, 
though it decidedly approaches nearer to C. Laburnum. The fibre elements of the 
xylem in C. purpureus are open and moderately thick walled ; dense, and with 
indurated shining walls in the others. From the figures it will be seen that the vasa 
of C. Adami essentially agree with those of C. Laburnum. 

The pith-cells of C. purpureus are very slightly thickened in their walls, with few 
pore areas, and accordingly show very delicate markings of shallow pits, while their 
outline is sharply polygonal. The cells of the other two are rounded and thick walled, 
so that they show correspondingly deep and well-marked pore canals. 

The above description proves that the hybrid part is most nearly like C. Laburnum 
in its stem configuration and upbuilding, but a very remarkable feature is revealed 
when careful preparations are made from the young epidermis of the three. We 
have already indicated that the epidermal cells of the hybrid approach most nearly 
to C purpureus in size and amount of cuticular thickening, but the manner in which the 
cell-nuclei of the two agree is quite striking, when we compare them with the nuclei of 
C. Laburnum. Plate VIII. figs. 10, 11, 12 illustrate these as perfectly as figures can. 
Alike after staining in aqueous eosin solution from the fresh living state, as after careful 
hardening in picric alcohol, the large spherical nuclei of the two former stain deeply, while 
they have a finely granular and spongy aspect. Those of C. Laburnum are small, shining, 
and pretty homogeneous in texture, even under very high powers, as if the chromatic 
substance of the nuclear membrane were specially abundant. The above description 
applies equally to the nuclei of the leaf epidermis. 

After satisfying myself that this held true of the epidermis, the idea occurred of com- 
paring the nuclei of internal elements, such as those of cortex, phloem, &c. So far this 
has been without result, as the nuclei vary greatly even in adjoining elements. But still 
it is very significant and suggestive that we should have tissues of one plant — no matter 
what its origin — with at least two very distinct types of nuclei in cells which work 
harmoniously together, so far as vegetative growth is concerned. This fact alone com- 
pletely demonstrates the extremely elastic adaptability of protoplasm and its modifications 
in the formation of vegetative structures. 

Leaf. — The three leaflets of the compound leaf of C. purpureus are small, elliptic- 
lanceolate, glabrous, and somewhat fleshy. Darwin (op. cit., p. 414) states that a twig 
of the purple form from a composite tree has " the leaflets a little broader, and the 
flowers slightly shorter, with the corolla and calyx less brightly purple" as compared 
with the ordinary species. There is a strong probability that this is a variation condition 
of some of the plants, just as the Dunkeld specimen has varied by becoming double in its 
" Adami " flowers, for while most that I have studied agree with Darwin's account, a 
branch bearing all three forms which was brought to me during the past summer by 
Dr Scott of Melrose agreed in the above, as in other features, with specimens of C. pur- 






MINUTE STRUCTURE OF PLANT HYBRIDS. 263 

pureus. The leaflets of C. Laburnum are large, elliptic-ovate, silvery-hairy beneath, 
and thin in texture, while those of C. Adami are elliptic, glabrous, less fleshy than in 
C. pur pureus but inclining towards C. Laburnum in size. 

Leaf. — (a) Petiole base. 

In C. purpureus the epidermis is devoid of hairs. The cortex underneath is a tolerably 
uniform cylinder of cells. A single crescentic bundle mass lies across the middle of the 
petiole; beneath and above it are broken, irregular masses of sclerenchyma, whose elements 
are small, measuring on the average 10 ll. Two small lateral bundles are also present. 

The phloem is 30 ll broad, and, in alcoholic material, of a very dark colour, due to the 
amount of tannin material in its elements ; its sieve tubes are 3 to 4fi across. The 
xylem is a single sickle-shaped band, whose main constituents are radially arranged rows 
of spiral tracheids, each on the average 8 ll across, while single radial rows of small dense 
cells lie between. 

In C. Laburnum the epidermis is abundantly clothed with the spindle-shaped hairs 
already referred to. The subjacent cortex has its outer cells modified in colloid manner, 
there being a single cell layer above which passes into two or three below ; internal to this 
is a pretty broad zone of uniform cells, succeeded by one to three layers of larger, looser, 
thin- walled cells, and this again passes into a broken sclerenchyma cylinder, made up of 
a deeply concave, inferior mass, and of smaller isolated patches external to the smaller 
bundles. The sclerenchyma elements average 15 //. across, though not a few may be 18 
to 20 ll. The bundle system consists of one large inferior concave mass and of two to 
three circular bundles, which almost touch each other. The entire bundle system, there- 
fore, forms a broken ring and encloses a quantity of what we may term pith tissue. 

The phloem is 55 to 65 ll deep, and is of a pale reddish hue in alcoholic material from 
the relatively small amount of tannin ; its sieve tubes are 6 m across. The xylem is an 
almost continuous cylinder whose spiral tracheids are 20 /x across, and between these are 
radial rows or irregular patches of cells. 

In C. Adami the epidermis has no hairs, as in the first, but otherwise the tissues 
take largely after the latter parent. The subjacent cortex has one layer of colloid cells 
above and two to three layers beneath ; these pass into large-celled, thin- walled tissue, and 
that again into sclerenchyma disposed on the whole as in C. Laburnum, though more 
sharply broken up into patches, thus inheriting the limited development seen in C. pur- 
pureus. Each element averages about 12 ll across. The vascular system is arranged as 
a broken cylinder, but the inferior part is deeper and stronger than the upper. 

The phloem in depth is about the same as in C. Laburnum, and the tint of it in 
alcoholic material is brownish-red ; its largest sieve tubes are 4 to 4'5m across. The 
xylem has spiral tracheids 14 to 15 n in diameter, which alternate with single or rarely 
double rows or patches of cells. 

In C. Laburnum, along the sides of the petiole base are isolated patches of stone 
cells, some being as much as 45 m across ; these are reproduced in C. Adami but are 
wanting in C. purpureus. 



264 DR J. M. MACFARLANE ON THE 

Leaf. — (b) Petiole one-third beneath insertion of leaflets. 

In C. purpureus the petiole at this region is greatly flattened out, so as to be 
crescent-shaped. Three to four layers of the cortex cells beneath the epidermis contain 
chloroplasts ; the sclerenchyma is principally produced as a crescentic band beneath the 
main bundle, and consists of one to two layers. Above the bundle it is feebly developed. 
The phloem is slightly concave, but the main mass of xylem is nearly flat. Two lateral 
bundles, which in position might be said to form the horns of the crescentic main bundle 
mass, repeat in miniature the arrangement of it. 

In C. Laburnum the outline of the petiole is circular, except that it is traversed on 
its upper face by a deep groove. Beneath the epidermis is a collenchyma layer and 
internal to it are one to two layers with chloroplasts, succeeded by four to five layers of 
pale large cells. The sclerenchyma and bundle masses are arranged as in the petiole 
base, but the two lateral bundles which have been given off from the cylinder lie superior 
to the sides of the cylinder, and repeat the arrangement of the deeply concave bundle in 
miniature. 

In C. Adami the outline of the petiole is most nearly as in C. Laburnum, though it 
is slightly flattened above and has only a shallow groove. A broken zone of collenchyma 
cells lies beneath the epidermis, and is succeeded by two or three layers of cells with 
chloroplasts, while three to four subjacent layers are large-celled. The sclerenchyma and 
bundle masses resemble those of C. Laburnum, though the elements are smaller and more 
feebly thickened. 

Altogether the entire petiole of C. Adami is very pronounced in its leaning towards 
C. Laburnum, particularly in the massing of tissue elements, so much so that one might 
on cursory examination conclude that the resemblance is complete. But many minor 
points throughout prove the modifying action which C. purpureus has had ; thus the 
difference in naked-eye outline, the incompleteness of the collenchyma layer, the reduced 
width of the large-celled layers, and the smaller size of the elements, are all to be 
explained as modified by it. 

Microscopically examined, the upper leaf epidermis of C. purpureus is almost identical 
with the lower (Plate VIII. figs. 4, 5) as to cell shape, number of stomata in a given area, 
and absence of hairs, though a very few of the last may be detected along the ribs. 

In C. Adami numerous stomata occur on the upper surface (Plate VIII. figs. 6, 7), 
though less abundantly than on the lower, being in the proportion of 4 : 5. In C. Labur- 
num the stomata are entirely confined to the lower surface, if we except a narrow patch 
on the upper epidermis, towards the base of the midrib and on either side of it. The 
hairs which spring from the lower epidermis (Plate VIII. fig. 9) are short, blunt, 
spindle-shaped, and minutely tuberculate, their presence giving a silvery sheen to the 
surface. I regard it as a point in favour of its exceptional origin that the "Adami" 
leaves should not have these in tolerable abundance. 

As regards relative distribution the stomata are as follows, under field of Zeiss' D 
with No. 2 eyepiece : — 



MINUTE STRUCTURE OP PLANT HYBRIDS. 265 

C. purpureus, upper epidermis = 27 to 30 stomata. 

„ lower „ = 30 ,, 

C. Adami, upper epidermis = 12 to 14 „ 

„ lower „ = 17 to 20 „ 

C. Laburnum, upper epidermis = (except a few along base of midrib). 

„ lower „ = 40 

The above gives us an average on upper and lower areas collectively of 58 to 60 in 
C. purpureus, of 31 to 33 in C. Adami, and 41 to 42 in C. Laburnum. 

The epidermal cell-nuclei of fresh or carefully hardened leaves agree as above noted 
with those of the stem. 

Cytisus Adami is probably unique, therefore, among plants in the possession of three 
totally distinct types of leaf, each of which can readily and certainly be distinguished by the 
naked eye, and in the possession of at least two distinct types of epidermal cell-nuclei. 

How far the hybrid part is a morphological adaptation as a mean between the two 
parent types for physiological work it would be no easy matter to verify, but whether 
we cau obtain indications of this in the epidermis or not, some countenance is given to 
the view when we study sections. 

Transverse leaf sections of C. Laburnum and C. Adami are thicker than those of 
C. purpureus in the proportion of 5 : 4. The palisade tissue of C. purpureus is quite 
continuous over the vascular bundle of the midrib, and beneath this is a very dense 
round-celled spongy parenchyma, so dense, however, that it scarcely merits the designa- 
tion " spongy." In C. Adami and C. Laburnum the palisade tissue is interrupted in 
continuity by a wedge-shaped mass of colourless cells which lie in the concavity of the 
leaf bundle ; the spongy parenchyma is loose in the last, but in C. Adami it very closely 
approaches C. purpureus in density. The vascular bundle of C. purpureus is small, 
flat or slightly concave upwards, and surrounded by loose round-celled tissue the upper 
layers of which lie below the continuous palisade parenchyma. The largest spiral 
tracheids of the xylem measure 7 v and the average are 5 m. The vascular bundle of 
C. Laburnum is large, semicircular, and demarcated from the surrounding laminar tissue 
by one layer of large, clear, rounded cells. The uppermost of these, along with the 
wedge-shaped mass of cells above mentioned, lie against the upper epidermis, and thus 
break the continuity of the palisade parenchyma. The largest spiral tracheids are 12 m 
across and the average are 9 /x. 

The bundle of C. Adami in shape, size, and relation to the surrounding tissue is like that 
of C. Laburnum, but the modifying action of C. purpureus is traceable in various ways. 
Thus the wedge-shaped cells that fill the concavity of the bundle show no thickening of 
their walls, while the zone of rounded cells that bound the bundle is only faintly indicated. 

Sepals. — The calyx of C. purpureus is entirely green ; that of C. Adami is largely 
green, but the tips of the sepals are semi-membranous ; that of C. Laburnum is green 
below, but by degrees becomes membranous above, the upper third of the calyx being 
entirely membranous. 

The inner (upper) surfaces of the sepals in C. purpureus and C. Adami resemble each 



266 DR J. M. MACFARLANE ON THE 

other in the development of many long unicellular hairs, alike along the veins and 
regions between. Those of C. Laburnum show a few hairs scattered near the apex of 
the teeth only. In C. purpureas and C. Adami there is a considerable number of 
stomata over the upper half of the calyx, three to four occurring under the D Zeiss 
objective, while in C. Laburnum stomata are quite absent. The epidermal cells of 
C. purpureus and C. Adami are chiefly quadrangular and straight walled below, but 
become very sinuous above, and are larger than in C. Laburnum, which has polygonal 
cells below that merge into elongated and slightly wavy cells above. 

The outer (lower) surfaces of the sepals in C. purpureus and C. Adami are glabrous ; 
in the first one to three stomata may be traced under Zeiss' D, in the second five to 
seven. The outer surface in C. Laburnum is densely covered with spindle-shaped hairs as 
over the vegetative leaves, and eleven to twelve stomata may occur over the above- 
mentioned area. 

The sepaline mesophyll tissue of C. purpureus shows in alcohol material a few dark- 
brown, sharply-defined chloroplasts ; in C. Adami they are more abundant, of a paler 
colour, and less sharply defined ; in C. Laburnum they are most plentiful, of a delicate 
neutral- tint colour, and have a soft, rather ill-defined aspect. The colour and relative 
sharpness of definition appears to be entirely due to tannin, which, existing probably as a 
tannate of albumen, is precipitated by alcohol. 

It may further be mentioned that along the margins of the sepals of C. purpureus 
and C. Adami there are not only long simple hairs but short spindle-shaped ones, with 
wart-like thickenings, such as we meet with in great quantity in C. Laburnum. 

Petals- — (a) Standard, — The comparative shape and venation of the three standards 
is well represented in Plate VIII. figs. 13a, b, c. The petals of C. Laburnum are glabrous 
throughout, but the hair distribution of the other two is specially worthy of note. At 
the junction of claw and blade in C. purpureus a line of hairs, about 125 to 130 in 
number, fringe the margin and are inclined outward and downward ; in C. Adami there 
are 60 to 65 similarly placed. These hairs, along with others placed on the same level, 
are evidently intended to guard the nectary entrances. 

The lower half of the standard in C. pmpureus is traversed on its inner side by a 
median groove, the bounding ridges of which are fringed by long, simple, intercrossing 
hairs. The epidermal cells of the claw are elongate and narrow, but gradually widen out 
upwards till above the middle of the petal they are quadrangular or polygonal. Their 
walls are wavy in outline and are infolded ; their free surface also is slightly convex. 

The lower half of the standard in C. Laburnum is likewise traversed by a groove, but 
its ridges are glabrous, the epidermal cells are like those of C. purpureus below, but 
higher up they are not only zigzag and infolded, each cell swells out into a cone-shaped 
papilla, and its surface is finely striate. In C. Adami the ridges which bound the groove 
of the standard are beset by simple hairs ; the epidermal hairs most closely resemble those 
of C. purpureus, but faint striae occur over the walls of the upper cells of the standard, 
as in C. Laburnum. 



MINUTE STRUCTURE OF PLANT HYBRIDS. 267 

Petals — (b) Wings. — Illustrations are given in Plate VIII. figs 13 a', b', c' . From these 
it will be seen that the claw in C. purpureus is slightly shorter than the blade, in C. Adami 
it is half as long as the blade, and in C. Laburnum rather less than one-third the length. 

Each wing in C. purpureus shows a twisted ridge on the claw which fits into a cor- 
responding groove on the claw of each keel-petal to form a locking spring arrangement. 
Along the upper edge, and to a less extent along the lower, there is a marginal fringe of 
long simple hairs, the number of the former being 160 to 170, and of the latter 30 to 35. 
The outer and inner epidermal cells are quadrangular-sinuous below, but gradually become 
more elongated and angular-sinuous above, where they develop infoldings of the walls. 
Their free surfaces are slightly convex. Each wing in C. Laburnum has a straight claw, 
and the only connection with the keel-petal is by a bulging depression in each, which fits 
the one into the other. The entire wing is destitute of hairs. The outer and inner 
epidermal cells are quadrangular or polygonal below, but they become very slightly wavy 
above, and their walls exhibit infoldings. The free surfaces of the cells along the upper 
half of each wing grow out into papillae. Each wing in C. Adami has a decided tw r ist on 
its claw, though it is not nearly so pronounced as in C. purpureus. Fringes of hairs 
occupy exactly the positions that they do in C. purpureus, but in all cases these are less 
abundant — thus one specimen had 130 along the upper margin and 14 below, another 76 
above and 17 below, a third had 83 above and 15 below, and a fourth had 73 above 
and 18 below. The epidermal cells are nearly polygonal below, but are almost exactly 
like those of C. purpureus above. They are further like the last, and quite unlike those 
of C. Laburnum in that they never form epidermal papillae, the free surfaces of the cells 
being merely convex. 

Petals — (c) Keel. — As shown by figs. 13 a", b" , c" of Plate VIII. , the relation in length 
the claw to the blade in the keel-petals is nearly in the same proportion as those of the 
wings. In C. purpureus a fringe of long hairs, 100 to 110 in number, grow out along 
the upper edge at the junction of claw and blade, and a long fringe of shorter feebler 
hairs, 300 to 330 in number, line the lower edge. The inferior epidermal cells are poly- 
gonal or rectangular and straight walled, but higher up they become elongate-sinuous. 
In C. Laburnum each keel-petal is destitute of hairs. The inferior epidermal cells are 
elongate and straight walled below, but higher up they become equiradial and sharply 
angular, with infoldings of the walls. In C. Adami fringes of hairs in the same position 
as those of C. purpureus line the margins of the keel-petals, but are half as abundant — 
thus one specimen had 48 to 50 along the upper edge, and 152 to 155 along the lower, 
another had 57 above and 148 below. 

Stamens. — The staminal tube of C. purpureus has two luxuriant lateral rows of hairs, 
and less abundant median masses. These hairs, like many of those on the petals, are . 
partly thin walled and uniform, partly provided with wart-like thickenings. The pollen- 
cells of alcoholic material are of a yellow-brown colour, and each is 25 to 26 [i. The 
staminal tube of C. Laburnum is entirely devoid of hairs. The pollen- cells are yellow in 
colour, and each is 21 to 23 /t. In C. Adami the staminal tube has two luxuriant lateral 

VOL. XXXVII. PART I. (NO. 14). 2 Q 



268 DR J. M. MACFARLANE ON THE 

rows of hairs, and also median ones, as in C. purpureus ; but both sets are less numerous 
than in the parent. The pollen-cells are of a pale reddish-brown colour, and each is 23 
to 25 fi. 

It has repeatedly been pointed out as a rather peculiar fact in connection with the 
high sterility of the hybrid parts, that the pollen-cells of it are mostly well formed. On 
Plate VIII. figs. 14 a, 14 b, and 14 c, illustrations are given of the three, and though two 
bad cells are figured from the hybrid, such are decidedly rare. 

Pistil, — In C purpureas the receptacular stalk and ovarian wall are quite glabrous. 
The circumstigmatic hairs when fully grown are very densely set, and the longest are 100 
to 120 fi. In C. Laburnum the receptacular stalk is glabrous, but the ovarian wall is 
densely covered with spindle-shaped hairs. The circumstigmatic hairs are rather loosely 
set, and are 160 to 180 ^ long. In C. Adami the stalk and ovarian wall are glabrous. 
The circumstigmatic hairs are more closely set than in the last, and the longest measure 
120 to 140 fji. 

The above results prove C. Adami to be even more unique in its minute anatomy 
than in its naked-eye characters, remarkable though these are. The promiscuous mixing 
up of tissue masses in the vegetative organs, such as stem, petiole, and lamina, and the 
union of these, so as to give a tolerably intermediate physiological result in cork formation, 
strengthening stays, sap conduction, and transpiration, is as curious as is the distribution 
of the secretions of a tannin nature throughout the composite organism, or of histological 
details in the floral organs. But the very striking resemblance which the epidermis of 
the hybrid portion has to that of C. purpureus, not only in the general structure of the 
cells, but in the size and structure of the cell nucleus, the distribution of the stomata, and 
specially of hairs, would seem at first sight to prove that the hybrid portion was wrapped 
round, so to speak, by an epidermis of C. purpureus. Other considerations, however, 
show that the effect of the Laburnum parent has been to swamp or reduce by half as 
exactly as we can estimate many of the " purpureus " peculiarities. Thus the number of 
stomata over one side of the leaf; the reduction, as a rule, by half in the number of the 
hairs over the floral parts ; also the reduction in size of the cells that form the floral parts, 
all give countenance to this. It is, nevertheless, remarkable that where hairs grow out 
from any epidermal surface in C. Laburnum, these should never be inherited by C. Adami, 
and conversely where hairs grow out from C. purpureus, these are always inherited by C. 
Adami, though reduced in number by about half. Still in Bryanthus erectus we have 
shown that an approach to this condition is observable. 

If, however, we select either stem or leaf, and go over seriatim the structural resem- 
blances or differences as compared with the parents, it will be found that, with the exception 
of the epidermis, the tissues have greatest affinity with C. Laburnum. But some seed 
hybrids, which we have described, may share in a similar one-sidedness of growth, though 
not to so exaggerated an extent, so that the gap separating graft from seed hybrids is 
not so wide as some have supposed. So far as the floral parts of C. Adami are concerned, 
these might quite pass for products of a well-balanced seed hybrid, and it is only in the 



, 



MINUTE STRUCTURE OF PLANT HYBRIDS. 269 

more truly vegetative regions that that strikingly diversified intermixture of tissues is 
found, which causes it to differ from all seed hybrids that I have studied. 

But the parents that were used for the production of the graft hybrid in the present 
instance are very unlike in habit, colour, &c, so that even a seed hybrid from them would 
be more than worthy to rank alongside Philageria ; and if the latter is sterile, need we 
wonder that this graft hybrid is also ? Were two species chosen, however, of close 
affinity, we suspect that a graft fusion as intimate as that just examined might bear 
perfect fruit in the hybrid part, and that such might reproduce a progeny as perfectly as 
do some of the seed hybrids. Thus a graft cross of TJlmus campestris and U. montana, 
of Fagus sylvatica and F. ferruginea, or of Betula alba and B. nigra, would probably 
give the desired result. This view is greatly strengthened when we recall the fact, 
already alluded to, that nearly all the pollen cells of C. Adami are good in appearance, 
though the ovules, according to Professor Caspary, are mostly monstrous. 

The flowers on the parent branches of the composite organism normally bear fruit 
almost or quite as abundantly as if each had grown independently, and the seeds give 
rise to plants like the parents, but the flowers on the hybrid branches never produce ripe 
fruit. This, we think, is a strong argument in favour of the hypothesis advanced in the 
latter part of this paper to account for relative sterility, if in the present instance we 
further suppose that the original plant resulted as a graft shoot from accidental union of 
the halves of a bud of each parent. Thus, if the grafter, in preparing the stock and 
shield, cut in half a vegetative bud along the margin of each where future union was to 
be effected, not only would the shield graft produce pure shoots from pure buds over its 
surface, but if union of the cellular tissue of each half bud of stock and graft respectively 
was accomplished, the product would be a composite bud, one side of which would ulti- 
mately form branches of C. Laburnum, the other of C. purpureus ; but along the 
junction surfaces union of protoplasm, of nuclear threads, and of chromatic substance 
might be effected so intimately that a hybrid tissue growth would ensue, showing admix- 
ture of structures characteristic of both parents. 

We are compelled to assume that a union of nuclei has taken place in view of the 
important role played by the nucleus in cell life, and also by the close resemblance which 
the flowers of C. Adami have to those of a seed hybrid which have thus resulted. 

Now, if such a composite growth were isolated and propagated, as was actually done 
according to M. Adam's account, the more copious and complex the branching and new 
bud formation became the more perfectly would admixture of the segregated cells of 
yellow, purple, and red parts become, without the necessity of their losing individuality. 
But just such an intergrowth and admixture would explain the histological peculiarities 
which we have met with in the vegetative parts of C. Adami. Though actual experiment 
and observation alone will decide the point, it seems to me essential for the production 
of such graft hybrids that halves of two buds should be united. Some have supposed 
that the formation of adventitious buds from the cambial layer in the region of graft 
union would best explain the requirements of the case. In view of observations such as 



270 DR J. M. MACFARLANE ON THE 

those of Hansen * on adventitious bud formation from previously permanent tissue, the 
above hypothesis is worthy of careful consideration, and it may even be that the contact 
of the two sets of cells of stock and graft causes a physiological stimulus analogous to 
that of fertilisation. But in all the experiments on graft hybridisation summarised by 
Darwin t the strong balance of evidence is in favour of fusion of half buds, except 
perhaps with Poynter's Rose, where a nearer approach to an ordinary seminal hybrid 
rather than to a composite plant, such as C. Adami, was obtained by what appears from 
description like adventitious bud formation. 

For the following reasons, then, we would regard C. Adami as a graft hybrid of 
pronounced type : — (1) Adam's account of its origin is perfectly natural ; (2) experiments 
on potatoes and hyacinths have in several cases produced organisms quite comparable to 
C. Adami; (3) while a few seed hybrids, such as Noble's Clematis and Berberis Neuberti, 
show an inclination to reversion in some of their parts to the parent type, we have none 
which present the pure parents growing side by side with the hybrid as an organism ; 
(4) the production of good and abundant seeds by the pure parts of the composite 
organism which yield offspring like those parts, is totally different from anything that we 
know of seed hybrids, though these do at times give rise to offspring some of which 
resemble one parent pretty strongly and some the other ; (5) that the segregation of 
mixed characters along with blending to an intermediate degree of others is unlike what 
we usually find in seed hybrids, though some of these show a tendency at times in this 
direction. 

In that case, we must admit, as pretty surely established, that cell unions may be 
effected without intervention of sexual elements, and that such unions can give rise to an 
organism, the flowers of which are not materially different from those of a sexual hybrid. 

V. General Summary of Results on Seed Hybrids. 

We may now briefly recapitulate some of the more evident or naked-eye characters of 
hybrids, and gradually pass to finer details. It has been demonstrated that in hair 
production, if the parents possess one or more kinds that are fundamentally similar, but 
which differ in size, number, and position, the hybrid reproduces these in an intermediate 
way. Illustrations of this were presented by Geum intermedium, Erica Watsoni, 
Cypripedium Leeanum, and Masdevallia Chelsoni. But if only one parent possess hairs 
over a given region the hybrid usually inherits these to half the extent, as in the petals 
of Dianthus barbatus and some floral parts of Bryanthus erectus. If the hairs of two 
parents are pretty dissimilar, instead of blending of these in one, the hybrid reproduces 
each, though reduced in size and number by half. The gland hairs of Saxifraga 
Andreivsii, the simple and gland hairs of Ribes Culverwellii, and those on the vegetative 
organs of Bryanthus erectus are examples. The peculiar case of hair distribution in 

* Abhand. d. Senckenb. nut. Geseli, Bd. xii. 

f- Animals and Plants under Domestication, 2nd edit., vol. i. pp. 419-422. 



MINUTE STRUCTURE OF PLANT HYBRIDS. 271 

relation to colour formation noticed in the sepal of Cypripedium Leeanum may also be 
noted here. 

In the formation of nectaries as traced in Philageria, Dianthus, Saxifraga, Ribes, 
&c, the above principles also hold. 

The distribution of stomata over any epidermal area has been proved to be a mean 
between the extremes of the parents, if the stomata of the parents occur over one surface 
or both, and if the leaves are similar in consistence, but, as in Iledychium Sadlerianum, 
and to a less degree in Saxifraga Andrewsii, if the stomatic distribution and leaf con- 
sistence differ in the parents, this may give rise to correspondingly different results in 
the hybrid. 

In amount of cuticular deposit, and arrangement of it into ridges or other localized 
growths, hybrids have been proved intermediate between the parents. We may merely 
recall here the case of Philageria stem, which inherited cuticular ridges from Lapageria, 
though reduced to half the size, since the Philesia parent was devoid of them. 

As Wichura has already proved for the vegetative leaves of hybrid willows, the 
venation of hybrid leaves is very uniformly intermediate between those of the 
parents. Figures are given with this paper of the vegetative leaves of Philageria and 
Saxifraga, and of the petals of Dianthus and Geum. The relation of the bundles to 
special terminations, as in the water stomata of Saxifraga. is in conformity with the 
venation. 

But the growth of tissue in a hybrid which is to determine the outline or angular 
position which any organ or part of one will assume is intermediate between those of the 
parents when the latter show traceable differences. Thus the sepals and petals, as also 
the styles and style-arms, of Geum intermedium, the floral parts as a whole of Saxifraga 
Andrewsii and Ribes Culverwellii, the frilling of some of the floral parts of Bryanthus 
and Cypripedium Leeanum are pronounced cases, while minor ones have been referred to. 

Turning to minuter anatomical details, every hybrid has yielded a large series of 
examples which prove that the size, outline, amount of thickening, and localization of 
growth of cell walls, is, as a rule, intermediate between those of the parents. We have 
repeatedly stated that as the outcome of growth localization, intercellular spaces of a 
hybrid are modified in size and shape as are the cells which surround them. Now this 
clearly demonstrates that the living protoplasm which has formed the cells is so organized 
in its molecular or micellar constitution that in every cell and over every infinitesimally 
minute area on its surface where cellulose is to be laid down the balanced effect of both 
parents is felt. 

Equally in the laying down of secondary wall thickenings, whether of a cuticularized, 
lignified, or colloid nature, numerous citations have been made where the amount and 
mode of deposition is evenly between the extremes of the parents. Perhaps the most 
striking case is that of the bundle-sheath cells of Philageria and its parents, where 
usually five lignified lamellae are traceable in each cell of Lapageria, eleven or twelve in 
Philesia, and eight or nine in Philageria. 



272 DR J. M. MACFARLANE ON THE 

In summarizing as to protoplasm and its modifications as plastids, where con- 
siderable differences can be traced in the plastids of two parents the hybrid gives 
excellent results. Only in a few parent plants have these differences been sufficiently 
marked to allow of comparison with the hybrid. The leucoplasts in the epidermal 
cells of the parents of Dianthus Lindsayi are very different in size, while most of 
the leucoplasts in the hybrid are exactly intermediate, but from careful measurement of 
lantern projection images of these it has been found that some very nearly resemble those 
of the female parent. The chromoplasts of the petal cells in Geum intermedium and of 
the sepal cells in Masdevallia Chelsoni are additional illustrations. Those of the former 
are very variable in size and number, but this is probably to be explained from its 
inheriting half of its hereditary features from Geum rivale, which is equally variable as a 
species. Leaves of corresponding age and position from Saxifraga Andrewsii and its 
parents have furnished chloroplasts of small size and dark green colour in one parent, of 
large size and soft emerald green colour in the other, and an intermediate type in the 
hybrid, though some diverge towards the " Geum " parent in having large chloroplasts. 

But the average size, shape, and lamellar deposition in starches of Hedychium 
hybrids are perhaps the most interesting cases adduced. When we remember that these 
are bodies formed temporarily as reserve food, and that they are built up by addition of 
successive micellae through the agency of minute protoplasmic masses or leucoplasts, we 
have a direct proof that these leucoplasts are themselves fundamentally modified. Their 
activity in the cells of the hybrid is evinced by the building up of starch grains which, 
though only of temporary duration in the history of the plant, are so accurately constructed 
as to be an exact combination in appearance of a half corpuscle of each parent. 

Finally, we may recall the facts advanced as to colour, flowering period, chemical 
combinations, and growth vigour, which, though scanty and fragmentary in their nature, 
all point to the conclusion that hybrids are intermediate between their parents in general 
life phenomena. 



VI. The Bearing of Hybridity on Biological Problems. 

A wide and attractive field for the biologist is still open in the investigation of plant 
and animal hybrids. Though much work of a laborious kind has been expended on 
the plant side, we must regard it merely as the small beginning to an inquiry that will 
yield results of great value. On the animal side it may truly be said that all the results 
are in the future. Such being the case, we can scarcely hope to do more at this stage of 
the inquiry than indicate shortly what seem to be lights cast on certain hitherto 
doubtful or intricate problems, from a minute study of plant hybrids. 

(a) Relative Potency of the Male and Female Sex Elements in the Formation of an 
Organism. — This problem has greatly occupied the minds of biologists during the last 
decade, and a solution has only been attempted hitherto from consideration of the 



MINUTE STRUCTURE OF PLANT HYBRIDS. 273 

behaviour of the sex elements at, and immediately subsequent to, the period of 
fertilisation. The tissues of hybrids shed a very exact light on the subject. No matter 
what tissue or set of tissues are chosen, if the cells composing such are tolerably diverse 
in the parents, one can trace with ease the modifying action which both sex elements 
have had on them, while these clearly prove to us that each sex element, after union 
with its complementary sex element, represents potentially half its former individuality, 
or retains half its former hereditary properties. If one select, for example, a few 
adjoining cells from the leaf epidermis of Dianthus Grievei and its parents, as figured in 
Plate IV. figs. 1-3, and compare these, one sees that the average cell of the hybrid is an 
exact mean between the cells of the parents. On comparing further the epidermal tissue 
of a dozen hybrids, if one were to be guided alone by the number of epidermal cells and 
of stomata over a given area, a like conclusion would be reached. In such special cases 
as the sepaline gland of Philageria and Lapageria, we deal with cells resulting from 
repeated division of a set of mother cells. To effect upbuilding of the hybrid 
gland, therefore, proliferation of a set of cells takes place, each of which has a Philesia 
heredity towards arrest of growth and a Lapageria heredity towards luxuriant cell 
proliferation, the resultant being a gland built up of half as many cells as that of the 
one parent. 

But Van Beneden * went further than most of his zoological co-workers were prepared 
to go when he asserted that each cell in an organism is a hermaphrodite structure. To 
this thesis many subsequently took exception, and with some show of reason perhaps, 
seeing that no direct proof in individual cell life was forthcoming. But one is forced to 
accept its absolute correctness from study even of one hybrid. It is this hermaphroditism 
of the entire hybrid organism which not only impresses on it the structure that the 
naked eye and microscope reveal, but which causes it to have a life cycle whose successive 
steps are intermediate between the parent extremes. Thus sufficient facts are in our 
possession, and will, we hope, be greatly supplemented ere long, to prove that the period 
of bud-bursting, of leaf-expansion, of flower production, fruit ripening, and other vital 
phenomena in hybrids are all dependent to a wonderfuHy exact degree on hereditary 
inheritance. Naturally, when we make this statement, we wish it to be clearly understood 
that secondary causes may modify or obscure the exactness of phenomena. Thus every 
one who is practically conversant with plant life knows the powerful influence which soil, 
moisture, situation, &c, have in altering the even tenor of a plant's way. It is on this 
account that we would earnestly desire to have continuous and exhaustive experiments 
carried out, where every possible care might be taken to eliminate disturbing factors. 

(b) Unisexual Heredity. — By this term we would designate the outcome of those 
observations now recorded which prove that structures found only in one parent, and with 
no corresponding counterpart in the other, are handed down, though reduced by half. 
The sepaline honey-gland of Philageria, the small circumstomatic cellular knobs of 
Saxifraga Andreivsii, the colour patches on the sepal of Cypripedium Leeanum, and the 

* Recherches sar la maturation de I'osuf, 1883. 



274 DR J. M. MACFARLANE ON THE 

spiral or spiro-reticulate thickenings on cells of Masdevallia Chelsoni, are observed 
cases. 

For the evolutionist these have some value. Whether one adopt the view that 
environmental surroundings are the main agents in conferring acquired characters, or 
that these wholly arise by accidental variation, we have strong grounds for believing that 
these acquired characters are handed down, though weakened in intensity by half. 
Nevertheless, if these are of advantage, sexual union of the progeny, coupled with possible 
further variation along the same line, may retain or even intensify the new character. 
But the case of Cypripedium Leeanum is of more than ordinary interest, for not only 
are the colour spots that are present in C. insigne and absent in C. Spicerianum inherited 
though in less intensity of tint, by the hybrid, but we find a complete absence of hairs 
where, under ordinary heredity transmission from C. Spicerianum, they should have been 
formed. Now it has been repeatedly noticed that when a species varies from the normal 
it seldom does so in one point or structural detail, but a certain variation- wave, so to 
speak, travels through the entire organism, giving it that combined set of characters 
which make it rank as a sub-species. The relation between colour production and hair 
distribution already described not only shows how new characters may be imported into 
a line of organisms, but how these may even be powerful enough to minimize the normal 
action of the other parent. A somewhat similar case is that of Saxifraga Andrewsii, in 
which the circumstomatic knobs inherited from the " Aizoon " parent are to all appearance 
correlated as a morphological character, with lime secretion by the stomata as a 
physiological one. 

(c) Bisexual Heredity. — The cases of such that have been noticed are few, and do not 
probably possess great interest apart from hybrid study. We include under this head such 
an example as Ribes Culverivellii, in which the simple hairs of R. Grossidaria and 
the oil-secreting peltate hairs of R. nigrum are both separately reproduced, though about 
half as large * as those of the parents. Saxifraga Andrewsii and Carduus Carolorum t 
likewise have distinct types of hair inherited from both parents. No cases are known to 
me where internal elements or tissue masses are thus separately reproduced. All the 
hybrids in which the above has been observed are derived from parents considerably 
removed in systematic relationship, and the incompatibility of blending the diverse types 
of hair probably explains their appearance as separate growths. 

But the general principle here illustrated on an exaggerated scale is that the offspring 
of two parents may inherit from each diverse peculiarities which, instead of blending 
evenly, retain their separate individuality. Future experiment and observation alone 
will decide for us whether these can be passed down through two, three, or more 
generations, and till we have the evidence it would be impossible to generalize. 

* I should state here that the gland hair figured from E. nigrum (Plate V. fig. 13) is slightly larger than the average, 
and that from the hybrid smaller, but for microphotographic work one has sometimes to choose material that shows the 
objects, even though these are not of average size. The cell details also are lost in the figure. 

t This is a very instructive hybrid that was gathered in Inverness-shire by Messrs Jenner and Howie, and of 
which abundant material has been secured for future description. 




MINUTE STRUCTURE OF PLANT HYBRIDS. 275 

(d) On the Divergence of some Hybrids, or Parts of Hybrids, toivards One Parent. 
— It is undoubted that not a few hybrids show a decided leaning towards one parent, 
though I consider from examination of several that have thus been described that the 
number has been considerably over-estimated. With undoubted cases we will now 
concern ourselves. Eegarding these many have asserted that the male parent or male 
element predominates, and sets up one-sided variation changes. We would readily grant 
both from perusal of Focke's " Pflanzen-mischlinge " and from direct observation that 
this is frequently true. But no one can deny that there are many artificial hybrids 
which do take more after the female parent. Professor Brookes,* recognising the 
strength of the former position, has formulated a theory of variation and heredity alike 
ingenious and plausible. In the present state of our knowledge we would not reject it, 
but we may still inquire whether some other and simpler explanation cannot be given. 

If we view the male and female sex elements of any plant as aggregations of a 
purely physical but very complex set of substances, it must necessarily follow that if the 
relative amount, or weight, or combination proportions, in each male or female element 
varies, variation will result after conjugation, and it will only be where the amount in 
each conjugating cell is an exact average of the producing organism that a new 
organism will develop which will show throughout an average combination of the 
characters of both parents. Now in the struggle for existence which holds among pollen 
cells and egg cells it will seldom happen that exactly the same amount of sex substance 
will be formed in exactly similar combinations in each. But of the two, which, we may 
ask, will vary most ? Direct observation proves that it is the male or pollen cell, and 
the reason for this is obvious. The great majority of flowering plants mature their 
ovules with the contained egg cells inside cavities where space for growth, and elaborate 
means for nutrition and protection up to the time of fertilization exists. But the 
opposite is the case with pollen cells, which are crowded together in the anther cavity, 
and often obtain nourishment by approximate sustenance through each other. Those 
therefore nearest the sustentative source will have the advantage, unless of course they 
are strongly pressed against by some firm bounding wall. 

I have been greatly surprised both with the average constancy in size of the 
egg cell and with the greater variability of the pollen cells in such plants as Lilium, 
Scilla, and Digitalis. But we now know that the nuclear substance is specially con- 
cerned in fertilization, and Strasburger has formulated a hypothesis t to account for 
diversities in hybrids by supposing that the two parents have a different average amount 
of chromatin substance in their sperm and egg nuclei. We would extend the hypothesis 
further, and regard the amount as a varying one even in the same parent. Hitherto I 
have not been able to measure the nuclei of sex cells, but in many vegetative cells there is 
clear evidence that the variability in size of the nucleus is very great, and further that 
there are considerable differences in the size of the nuclei and nucleoli even in adjoining 
cells. So much is this the case that I have felt quite safe only in comparing the 

* The Laio of Heredity, Baltimore, 1885. t Neue Untersuchungen, p. 163. 

VOL. XXXVII. PART I. (NO. 14). 2 R 



276 DR J. M. MACFARLANE ON THE 

nuclei of Cytisus Adami with those of its parents. Now if this be true of vegetative 
cell nuclei, there is strong probability that it will equally hold with reproductive nuclei, 
and accordingly the greater resemblance of any resultant embryo to one parent over 
another would be satisfactorily explained on a physical basis. 

But this does not on first look enable us to explain those cases where local 
divergences toward either parent occur in a hybrid which otherwise is very evenly 
balanced. Many examples of this have cropped up in the course of investigation and 
description. But an application of the same hypothesis in its minuter bearings will clear 
away most difficulties. If we view a fertilized egg of any plant which is about to 
segment to form an embryo as being not merely a chemically complex nucleated mass of 
protoplasm, but as a microcosm in which the orderly-arranged molecules of the conjugated 
male element have so exactly fitted into and become united with corresponding molecules 
of the female element that after conjugation co-ordinated groups of molecules are set 
apart as stem-producers, root-producers, leaf-producers, and hair-producers, we will have 
done much to clear away obstacles. But physically there is no reason why we may not 
assume that each cell of the future ]3lant has representative molecules in the apparently 
simple egg. Now if such be the case it may not unfrequently happen that corresponding 
groups of molecules from male and female cells do not unite exactly owing to incomplete 
nutrition or other defect in the maturing of one group. Thus one of the two may in 
part break down or become weakened and the complemental sexual part thereby give to 
the resulting tissue a one-sided character. Since the nuclear substance of the male or 
pollen cell is the one most liable to variable development through over- or under- 
nutrition, or through advantageous or disadvantageous position, it follows that variation 
will oftenest have its expression from the male side. 

(e) Mechanical or Physiological Obstacles to Fertilization as an Explanation of 
Infertility in some Hybrids. — Great importance has been attached by many to the fact 
that some parent species which ajDpear even to be nearly related refuse to cross, or only 
do so on one side, reciprocal crosses being apparently impossible. But as Strasburger 
has well emphasized '* a very simple mechanical explanation like that advanced on the 
animal side by Pfluger in the case of Amphibians may explain the difficulty. Thus it 
is possible that the sperm nucleus, or pollen tube containing such, of some plant 
species may be too large for the receptive area of the egg cell or ovular surface, though 
the opposite application might prove quite fertile. Similarly the relative length and 
shape of style, size of pollen grain, strength of pollen coat, amount of mucilage secreted 
by the stigma, time of ripening of stamens and stigma, must all be studied before we 
pronounce any attempted hybrid union impossible. Equally simple physiological 
obstacles connected with colour or some special chemical production may help in 
explaining partial or entire sterility. When treating of Cytisus Adami we noted a great 
abundance of tannin material in the " purpureus " parent, a relatively small quantity in 
the " laburnum " parent, and an intermediate amount in the hybrid. This extended even 

* Neue Untersuchuiujcn, p. 194. 



MINUTE STRUCTURE OF PLANT HYBRIDS. 277 

to the pollen grains, and gave to each a certain and recognizable tint. Now we know that 
repeated attempts to cross C. purpureus and C. Laburnum have failed, and it is quite 
possible that the action of the abundant tannin material on the stigma or egg cell of C. 
Laburnum, and vice versa the small amount of it for C. purpureus, may largely explain 
the failures. Many of the negative hybridization experiments of the past therefore may 
have less depth of significance than one is inclined on first view to attach to them. 

(f) On the Relative Fertility of Hybrids in Relation to Heredity. — The concensus of 
opinion among the older hybridizers was that very few hybrids were fertile, and that 
those which were, gradually returned to one of the parent types. During the last 
twenty or twenty-five years the opinion has been freely criticised, and rightly so, since 
horticulturists in that period have carried forward experimental hybridization by leaps 
and bounds, and have imported through intelligent collectors not a few wild plants which 
they regarded as, and in some instances have proved to be, natural hybrids. 

But even though the subject of pollination, with all the marvellous floral adaptations 
for it, were unknown to such experimenters as Kolreuter, Knight, Gartner, Wichura, 
and others, the main outcome of their researches can scarcely be set aside, though we 
may have to give a more liberal interpretation to it in the future. To sum up present- 
day experiences, it may be said that crosses between species that are nearly related in 
structure and habit can readily be effected, and the offspring may be largety fertile, at 
least among certain genera. Crosses between species that differ considerably in form, 
flower-colour, and habit are more difficult to perform, and the hybrids are largely sterile, 
while crosses between such divergent species or genera as Dianthus alpinus and 
barbatus, Saxifraga Geum and Aizoon, Lapageria and Philesia are almost or wholly 
sterile. 

Now when the pollen and egg cells from each of these three roughly classified groups 
are examined one finds that a few of those from the first are shrivelled-looking and badly 
formed ; from the second a considerable percentage are thus affected ; while from the 
third it is difficult to get one good pollen grain, and rather difficult to get one well-formed 
egg-cell, though these do not appear to be so much affected as the pollen grains. 

We have repeatedly referred to, and in Plate V. fig. 10 6 have illustrated a bad pollen 
sample. The cells are always smaller, often greatly smaller, than in either parent ; the 
protoplasm is devoid of rich nutritive granules and is scanty in quantity, so that it does 
not fill the cell cavity, the wall is irregular in outline and imperfectly formed. Shortly, 
therefore, it may be said that while the vegetative cells of a hybrid can develop gradually 
into organs that are a blended reproduction of those of the parents, the generative cells 
fail to receive or to form appropriate protoplasmic material. 

Consideration of this causes us to look at the theories that have been advanced to 
account for heredity. Darwin's theory of pangenesis has been put aside as cumbrous 
and difficult to conceive of in practice, though it explained phenomena of heredity all 
along the line better than any previously existing view. More applicable, however, docs 
Nageli's idioplasmatic theory appear, in spite of gratuitous assumptions that have been 



•278 DR J. M. MACFARLANE ON THE 

urged against it. The fundamental idea animating the pangenetic theory is that the sex- 
eells are the cumulative expression of all the actions and reactions, the integrations and 
disintegrations which have been associated with the protoplasms up to the time when 
these sex-cells have been fully formed. Nageli in expressing the same fundamental idea 
brought it more into line with modern cell discovery by assuming that the nucleoplasm 
was a continuous network. Weismann has objected to Nageli's hypothesis * as follows : — 
" The idioplasm does not form a directly continuous network throughout the entire 
body," and " it is perfectly certain that the idioplasm cannot form a continuous network 
throughout the whole organism if it is seated in the nucleus and not in the cell-body." 

But it may well be asked, How do we know that idioplasm, nuclear substance, nucleolar 
substance, or chromatic substance, is not connected into one network ? A dozen years 
have not passed since the majority of biologists would have rejected the idea of an 
intercellular network. Our minds should be open to receive fairly any hypothesis, 
or facts favouring a hypothesis, that may be presented without dogmatising that such 
cannot be. 

We repeat it, then, as an observed fact, that the reproductive cells of hybrids are to a 
greater or less extent small, imperfect, and badly formed, and that the more divergent 
the parent types the more numerous do the imperfect cells become. If with Weismann 
we view each of these as descendants from the germ-plasm of the hybrid egg, why do 
these fail to mature and continue the hybrid progeny ? It may be replied that the 
susceptible germ-plasms refuse to blend, or blend so imperfectly, that while the blended 
somatoplasms develop the vegetative part of the. hybrid, the germ-plasms break down. 
But this compels us to assume a greatly more cumbrous state of matters than does the 
pangenesis theory, for we must suppose that these imperfectly blended masses of germ- 
plasms are carried up with the growth of the stem, and finally appear at the floral 
extremities in an aborted state, and that this continues year after year in a hybrid shrub 
or tree ; and we must further assume in the case of Cytisus Adami, that the same is 
effected by vegetative union of the parts of two parents, without the intervention of 
sex-cells. It may be urged in the latter case that some germ-plasm cells were mixed up 
amongst the apparently pure vegetative or somatoplasmic cells, but even if this be 
granted, it still proves that a hybrid growth can develop apart from sexual union. We 
believe that a simple and more natural explanation can be given, a short summary of 
which has already appeared in Nature(vol. 44, 1891). 

(g) Vegetable Cell Structure in Relation to Hybridity. — Observations made by me, 
alike on resting and dividing cells, during the last few years, and preparations which Mi- 
Mann made and kindly showed me, caused me to adhere to my already published views on 
cell-life, viz., that in the ordinary resting state of an active cell, i.e., one capable of, and 
at times showing, division, a nucleus with nucleolus and endo-nucleolus are integral parts, 
and that after division of the cell has ceased proliferation of the inner parts may still go on 
leading to a multi-endonucleolar, then to a multi-nucleolar, and finally to a multi-nuclear 

* Biological Memoirs, first English ed., pp. 180, 181. 



MINUTE STRUCTURE OF PLANT HYBRIDS. 279 

state.""" In certain rare cases, e.g., endosperm cells, proliferation of the nucleolus may 
produce a temporary multi-nucleolar state, while the nucleus and cell can divide at a later 
period. Behaviour of the endo-nucleolus and nucleolus during division causes me to regard 
these as the special cell-centres, and this is well illustrated in species of Spirogyra, where 
the whole role of nuclear division is subsidiary to the nucleolus, and is only initiated subse- 
quent to indications of commencing division in it.t We regard this as the true explanation 
of division processes in other plant cells. Now in Spirogyra one can readily see that the 
nucleolar material not only forms the main mass of chromatic substance, but that it is 
connected by an extremely fine network system with the nuclear membrane, which is also 
chromatic, and during division breaks down to fuse with the radiating threads from the 
nucleolus. In re-formation of the daughter nuclei also round the daughter nucleoli, the 
nuclear membrane gradually reappears, first on the outer poles or nuclear faces, but some 
of the nucleolar threads can be traced to radiate out through and beyond the nuclear 
membrane and across the cell-cavity to the pyrenoid centres. Now, in my earlier studies of 
Spirogyra^ I was puzzled to understand how these radiating threads that were originally 
continuous in the nuclear spindle seemed to separate as deposition of the cell-septum took 
place between. Recent careful study with high powers reveals that from the pyrenoid 
centres of some bands extremely fine chromatic threads stretch across to, and connect, 
the pyrenoid centres of other bands. A connection of these from one ceil to another has 
not as yet been traced, but, apart from observations on other plant-cells which favour 
it, the strong probability is that such exists, for this network is quite continuous 
during division up to time of deposition of the cell-partition, and as the latter is 
laid down by union of micellae from the peripheral protoplasm and from the spindle 
threads, these may retain delicate continuations of their substance through the formed 
partition. 

We would consider, then, that the nucleolus is the special chromatic and cell centre ; 
that it sends out fine radiating processes — the intranuclear network — which partially 
fuse externally to constitute the nuclear membrane, the interspaces of the network being 
occupied by nucleoplasm concerned in metabolic change ; that radiating continuations of 
the chromatic substance pass out beyond the nuclear membrane, and form a network in 
the protoplasm, while we would suggest for future proof or disproof that they further 
may be continued through wall pores to form an intercellular chromatic connection. 

Not only in Spirogyra but in leaf cells of Dioncea and of Masdevallia radiating 
chromatic threads have been traced. 

The question now arises as to the nature and origin of the chromatic substance. 
This is pretty generally viewed now by biologists as sexual substance par-excellence, and 
as being the bearer of hereditary characters. To explain its distribution in each cell, we 
may consider with most biologists that the simplest plant and animal cells have no 

* Trans. Roy. Soc. Edin., vol. xxx., 1881-82. 

+ Confirmatory observations on two species of Spirogrjra will shortly be published, giving details. 

X Trans. Bot. Soc. Edin., vol. xiv., 1882. 



280 DR J. M. MACFARLANE ON THE 

nuclear differentiation, and consist of an apparently simple protoplasmic mass. But the 
power of movement, of digesting and assimilating food-particles, of retreating from 
centres of disturbance or irritation, &c, would cause us to inquire whether the apparently 
undifferentiated mass is not traversed by a fine protoplasmic reticulum of a neuromuscular 
kind. Such is the view that many have held and still hold. 

But unicellular forms that show sexuality show also a nucleus, nucleolus, and 
endonucleolus, the two last being often and carefully figured by Butschli, Huxley, and 
others, while we consider their occurrence as universal in all cells of sexual plants and 
animals. We have, however, already asserted our conviction that the nucleolus is the 
important cell centre, and we have further proved by hybrid investigation that every 
cell of an organism is hermaphrodite. Let us suppose, for attempted explanation, that 
the nucleolus with its radiating chromatic threads is purely sexual, and is made up of the 
fused chromatic constituents of male and female cells. Let us suppose further that the 
nucleolar or sexual substance is gathered round a central differentiation or aggregation of 
the protoplasmic reticulum, which might be the endonucleolus, and that it sends out 
radiating chromatic processes along these threads which in part anastomose into a fine 
chromatic layer — the nuclear membrane — so as to enclose in the interstices of the meshwork 
system a quantity of nutritive protoplasm which is at once a bed for the nucleolus and a 
feeder of it. Other radiating chromatic threads continued from the nucleolus and passing 
beyond the nuclear membrane would ramify minutely through the protoplasm along the 
threads of the reticulum, giving such appearances as we have traced in Spirogyra, 
Masdevallia Veitchiana, Ornithogalum pyramidale, and Dioncea. 

The hypothesis would enable us to explain much that is at present involved and 
obscure, while it would also enable us to dispense with the need for germ plasms. It 
would permit us to entertain the possibility of a comparatively rapid intercommunication 
of particles, and an even more rapid propagation of external stimuli, from cell to cell 
accompanied by change in every molecule reached by these stimuli. The sum-total of 
these would be expressed in the sex-cells, wdiich are the slowest to mature. 

We would thus view a plant as a group of connected hermaphrodite cells, 
descended from a fertilized egg-cell, and bound together by a fine chromatic 
ramification, the centre of which in each cell is the nucleolus. This chromatic system, 
intimately in contact with the general protoplasm, would receive stimuli and nourishment 
from it, while the combined action of these and other agents would tell not on one cell 
or cell-group, but be shared to a greater or less extent by all. 

The above view does not compel us to suppose that the older cells in which the 
nuclei are carried round in the protoplasmic current are thus connected, for these have 
passed the stage of active division, and have their permanent life functions already 
expressed. 

If we apply the above views to explain the frequent sterility of hybrids, a possible, or 
we may venture to say, a probable hypothesis can be framed. If each reproductive cell 
of an organism is specialised as an epitome of the individual which produces it (and in 



MINUTE STRUCTURE OP PLANT HYBRIDS. 281 

spite of arguments advanced by Weismann and his school, we adhere to Darwin's widely 
collected facts and reasonings on them as entirely favouring this), and gathers up the 
features of that individual in its development and maturation owing to the constant 
action and reaction between its chromatic substance and that of co-organismal cells, 
it follows that for the accomplishment of this there must be a certain co-ordination or 
rhythmic harmony in the motion of the molecules, and an appropriate attraction — 
chemical or otherwise — in the combining molecules. If otherwise, then instead of 
integration of molecule to molecule, disintegration or at least an incapacity for union will 
hold. 

But it should here be emphasized that reproductive cells are greatly more concentrated 
in their history than ordinary vegetative cells, and only attain their full maturity after 
the active stage has been passed in the last, or, as Professor Ryder has well put it in 
his suggestive paper on the subject, "Sexuality begins when growth ends."* This 
does not, however, interfere with the fact that sex-cells are often cut off at a very early 
period from the vegetative ones, for the former may then undergo, as we know them in 
many cases to do, a slow maturing process, and be greatly acted on or modified by the 
latter. Now we know that the most impressionable time in the history both of plants and 
animals is that of growth — not of maturity — and therefore the experiments which may 
have been instituted on animals, and such arguments as those bearing on exercierknochen, 
&c, are practically worthless, because the individuals practised on have not in most cases 
been treated from the earliest impressionable period, when the substance of the sexual cells 
is in process of formation. It should be noted also that in the human subject and other 
mammals the eggs are observable in the Graffian follicles at birth, and yet are not 
matured and shed till years of slow upbuilding and moulding action have affected them. 

If we return now to hybrid production of the more extreme types, though in virtue 
of the attraction which exists between sexual elements, the original male and female 
cells from parents of different species — in the absence of cells from the same species — 
may be capable of uniting, and, in the process, of overcoming the repulsion due to 
dissimilar co-relative molecules in each, when the attempt is made by all the hermaphrodite 
cells of the resulting hybrid organism to concentrate representative hermaphrodite groups 
of molecules, many cases will occur in which these will blend imperfectly, owing to 
differences in the composition and amount of chemical substances present, or interference 
and cancelling effects due to unequal propagation of waves of motion between the 
molecules. Thus many groups of molecules will break down or fail to reach their 
destination, so that gaps or vacancies will occur in the organic completeness of the pollen 
or egg cell. It will then have the shrivelled half-empty look so characteristic of 
hybrid sex-cells that are sterile. In hybrids from more nearly related species the 
interfering or cancelling effects will be reduced in proportion, and a larger number of 
sex-cells will have a chance to mature. 

(h) Value of Microscopic Characters in the Future Verification of 'Doubtful Hybrids. — 

* " The Origin of Sex," Proc. Amer. Phil. Soc, vol. xxviii. 



282 DR J. 351. MACFARLANE ON THE 

We have advanced reasons, drawn from microscopic study as well as from other points of 
view, that Bryanthus erectus is a true hybrid, and that its reputed parentage is correct. 
In the progress of horticulture, forms are continually appearing which are asserted to 
be hybrids, and similarly as reputed wild species or varieties are being more carefully 
scrutinised their hybrid nature is at times suggested. The great difficulty in safely 
determining whether this is so has been the absence of sufficiently marked naked-eye 
characters in the parents and hybrid. In a valuable contribution to hybridity by Mr 
Meehan # many plants are mentioned which Linnaeus looked upon as hybrids between 
species, but which he nevertheless described as species since the}^ freely reproduced 
themselves. From a rather hasty study of some of these we should be inclined to 
question Linnaeus' verdict in their case, but such forms as Trifolium hybridum, present 
an apparently strong case for the systematise Armed now with an increased range 
of characters for comparison, it should be possible to decide whether some at least have 
not an undoubted relation to the supposed original parents. In such cases, nevertheless, 
it must be kept in mind that if their origin dates back over a long period such changes may 
subsequently have been effected in them by variation and selection that the comparison 
can only be approximate, unless indeed one were to produce the hybrid artificially, and 
find close microscopic resemblances between the natural and artificial types. In any case 
we consider it as undoubted that recognition of hybrids from careful microscopic study 
should now be possible in the great majority of cases. 

(i) The Possible Origin of Species from Hybrids. — When the literature of hybridity 
perused from the historical standpoint one cannot fail to be impressed with the more 
liberal spirit in which the subject is treated, and with the increasing belief in hybrids that 
are tolerably, or even very fertile. Specially is this so on the botanical side, but a paper by 
the late Francis DAY,t from the zoologists' standpoint, proves that great interest will 
centre round the subject at no distant date. Hitherto it may be said that authorities, 
with few exceptions, have declared wholly against the view that hybrids may be 
sufficiently fertile, and their progeny sufficiently strong and adaptable to be fitted for 
survival, not to say increase, in the struggle for existence. The admirable experiments 
conducted by Wichura on willows go far to prove, one would think, that by the fourth 
or fifth generation enfeeblement and decay become so marked that continued production 
fails. But against this is to be placed the fact that many of our horticulturists are 
ardent believers in the continued fertility of hybrids, as witness the article by Professor 
Meehan already cited, though we believe that an over-sanguine expectation is some- 
times entertained under this head. 

When one finds the undoubted hybrid between Geum rivale and G. urbanum 
frequently described by systematists as a species, and that in many places the hybrid is 
nearly or quite as abundant as either parent, that it freely produces good seeds, and further 
that it has, as we have already indicated, many points of superiority as a combined 

* The Independent, No. 1063, New York, 
t Proceedings of the Cotteswold Club, 1888-89. 



MINUTE STRUCTURE OF PLANT HYBRIDS. 283 

organism which neither parent possesses separately, we have good reason for the exercise 
of caution before pronouncing decisively against species production from hybrids. Still 
it must be confessed that our experimental statistics are so meagre and unsatisfactory that 
no final opinion can be given. In saying this we do not in the least under-estimate the 
conclusions arrived at by Kolreuter, Gartner, and their successors, but the wonderful 
effects of altered conditions of soil, climate, and situation in giving relative fertility to 
hybrids that were formerly regarded as sterile were not fully recognized in their day, and 
are only now being to some degree appreciated. 

Strong reasons can be urged for the prosecution of careful and prolonged investiga- 
tions on the subject in our botanic gardens, experimental stations, and private gardens. 



Though a partial investigation has already been made, no account has been taken in 
this paper of second or third hybrids, or of hybrids in which, by reciprocal crossing, 
different results are got. These will be treated of in a subsequent paper. 

The author gladly acknowledges the help received from various quarters since 
commencement of this investigation. Valuable supplies of material have been received 
through the kindness of the Directors and Curators of Kew, Glasnevin, Edinburgh 
and Glasgow Botanic Gardens, and from many private sources. The constant aid 
extended by Professor Balfour and Mr Lindsay deserve special mention, while Mr 
Kichardson and Mr Forgan have given valuable help and advice on micro-photographic 
details. Through the generosity of the Botanical Committee of the Eoyal Society, 
a grant was given for purchase of material and illustration of the paper. 



October 1891. 



Explanation op Plates. 



VOL. XXXVII. PART I. (NO. 14). 2 S 



284 DR J. M. MACFARLANE ON THE 

DESCRIPTION OF PLATES I.-VIIL, 
Illustrating Dr J. M. Macfarlane's Paper on " Plant Hybrids." 

Plate I. 

Fig. 1. Transverse section, root of Philesia buxifolia, x 50°. e., epidermis ; ex., external cortex ; i.e., internal 

cortex ; b.s., bundle sheath. 
Fig. 2. Transverse section, root of Philageria Veitcliii, x 50°. Letters as above. 
Fig. 3. Transverse section, root of Lapageria rosea, x 50°. Letters as above. 
Fig. 4. Transverse section, external root-region of Pfiilesia buxifolia, x 450°. 
Fig. 5. Transverse section, external root-region of Philageria Veitcliii, x 450°. 
Fig. 6. Transverse section, external root-region of Lapageria rosea, x 450°. 
Fig. 7. Transverse section, central root-region of Philesia buxifolia, x 450.° i.e., cells of the inner cortex; 

b.s., indurated cells of the bundle sheath ; ph., phloem patch ; v.a., pitted vessel of the xylem. 
Fig. 8. Transverse section, central root-region of Philageria Veitcliii, x 450°. Letters as above. 
Fig. 9. Transverse section, central root-region of Lapageria rosea, x 450°. Letters as above. 
Figs. 10a, 106, 10c. Highly magnified views of bundle-sheath cells from Philesia, Philageria, and Lapageria 

respectively. 

Plate II, 

Fig. 1. Transverse section, stem of Philesia buxifolia, x 50°. e.-, epidermis; co., cortex; s., sclerenchyma sheath. 

Fig. 2. Transverse section, stem of Philageria Veitcliii, x 50°. Letters as above. 

Fig. 3. Transverse section, stem of Lapageria rosea, x 50°. Letters as above. 

Fig. 4. Transverse section, external stem-region of Philesia buxifolia, x 450°. ca., cuticle of the epidermis. 

Fig. 5. Transverse section, external stem-region of Philageria Veitcliii, x 450°. 

Fig. 6. Transverse section, external stem-region of Lapageria rosea, x 450°. 

Fig. 7. Transverse section, bundle and matrix parenchyma of Philesia buxifolia, x 550°. ph., sieve tubes of 

phloem ; 75a:., protoxylem. 

Fig. 8. Transverse section, bundle and matrix parenchyma of Philageria Veitcliii, x 550°. Letters as above. 

Fig. 9. Transverse section, bundle and matrix parenchyma of Lapageria rosea, x 550°. 

Plate III. 

Figs. 1, 2, 3. Illustrations of skeleton leaves of Philesia, Philageria, and Lapageria ; nat. size. 

Fig. 4. Upper leaf epidermis of Philesia buxifolia, x 150°. The cells here shown are less thickened in 

their walls and slightly more sinuous than in the mature tissues ; but difficulty of photographing 

successfully mature epidermal tissue compelled the use of this. 
Fig. 5. Upper leaf epidermis of Philageria Veitcliii, x 150°. Though closely resembling fig. 4, the average 

condition approaches more towards fig. 6. 
Fig. 6. Upper leaf epidermis of Lapageria rosea, x 150°. 
Fig. 7. Lower leaf epidermis of Philesia buxifolia, x 150°. 
Fig. 8. Lower leaf epidermis of Philageria Veitcliii, x 150°. 
Fig. 9. Lower leaf epidermis of Lapageria rosea, x 150°. 

Fig. 10. Longitudinal median section through base of outer perianth segment (sepal) of Philesia buxifolia, x 25°. 
Fig. 11. Longitudinal median section through base of outer perianth segment of Philageria Veitchii, x 25°. 

gl., gland tissue. 
Fig. 12. Longitudinal median section through base of outer perianth segment of Lapageria rosea, x 25°. 

gl., gland tissue. 






MINUTE STRUCTURE OP PLANT HYBRIDS. 285 



Plate IV. 

Fig. 1. Upper leaf epidermis of Dianthus alpinus, x 120°. 

Fig. 2. Upper leaf epidermis of Dianthus Grievei, x 120°. 

Fig. 3. Upper leaf epidermis of Dianthus barbatus, x 120°. 

Fig. 4. Lower leaf epidermis of Dianthus alpinus, x 120°. 

Fig. 5. Lower leaf epidermis of Dianthus Grievei, x 120°. 

Fig. 6. Lower leaf epidermis of Dianthus barbatus, x 1 20°. 

Fig. 7. Transverse section, stem of Dianthus alpinus, x 85°. e., epidermis ; eo., cortex ; c, cork ; i.e., inner 

cortex; ph., phloem; ca., cambium; x., xylem. 
Fig. 8. Transverse section, stem of Dianthus Grievei, x 85°. Letters as above, s., sclerencbyma, absent in last. 
Fig. 9. Transverse section, stem of Dianthus barbatus, x 85°. Letters as above. 

Fig. 10. Surface view of leaf epidermis from Dianthus alpinus, stained in watery eosin, x 450°. I., leucoplast. 
Fig. 11. Surface view of leaf epidermis from Dianthus Grievei, x 450°. 
Fig. 1 2. Surface view of leaf epidermis from Dianthus barbatus, x 450°. 
Figs. 13a, 136, 13c. Petals of Dianthus alpinus, D. Grievei, and D. barbatus; nat. size. 
Figs. 14a, 146, 14c. Outlines of nectar glands from above plants, exposed in longitudinal section. 

Plate V. 

Figs, la, 16, lc. Transverse sections, roots of Geum rivale, G. intermedium, and G. urbanwm, showing cork 

layers formed during successive years. 
Fig. 2. Maturing achene of Geum rivale, x 8°. The style-arm (s.a.) projects as a rounded knob (s.a.k.) at its 

attachment to the tip of the style (s.). 
Fig. 3. Maturing achene of Geum intermedium, x 8°. The style-arm (s.a.) has a slightly projecting knob, as 

has also the style at the point of attachment of the two. 
Fig. 4. Maturing achene of Geum urbanum, x 8°. The style (s.) projects as a rounded knob (s.k.) at its attach- 
ment to the style-arm (s.a.), which is devoid of any projection. 
Figs. 5a, 56, 5c. Petals of above three plants ; nat. size. 
Figs. 6a, 66, 6c. Pollen grains of above three plants, x 400°. Two small bad grains are shown from the 

hybrid (66), though these compared with the good grains are greatly in the minority. A bad one 

from Geum rivale is seen in fig. 6a. 
Fig. 7. Transverse section, stem of Ribes Grossularia, x 75°. e., epidermis; eo., outer cortex; c, cork; i.e., 

inner cortex; ph., phloem; x., xylem. 
Fig. 8. Transverse section, stem of Ribes Culverwellii, x 75°. Letters as above. The specimen figured was 

from a thick twig, and the cork development has been excessive. 
Fig. 9. Transverse section, stem of Ribes nigrum, x 75°. 
Figs. 10a, 106, 10c. Pollen grains of above three plants, x 350°. 
Figs. 11, 12, 13. Surface views of under leaf epidermis of above plants. Fig. 11 x 150° ; Fig. 12 x 150° ; Fig. 

13 x 200°. 

Plate VI. 

Figs. 1, 2, 3. Leaves of Saxifraga Geum, S. Andrewsii, and S. Aizoon, clarified to show disposition of vascular 
bundles to water stomata ; nat. size. 

Figs. 4, 5, 6. Surface views of water stomata and surrounding tissue from above three plants, x 450°. Saxi- 
fraga Geum is devoid of circumstomatic knobs, the hybrid has sixteen of these in the figure, and 
8. Aizoon has thirty. 

Figs. 7a, 76, 7c. Petals of above three plants, slightly enlarged from nat. size. 

Figs. 8, 9, 10. Longitudinal sections of flowers of Saxifraga Geum, S. Andrewsii, and S. Aizoon, x 50°. 
s., sepals. These sepals are strongly reflexed in fig. 8, form an angle of 120° with continuation of 
the main axis in fig. 9, and an angle of 30°-35° in fig. 10. 



286 MINUTE STRUCTURE OF PLANT HYBRIDS. 



Plate VII. 

Fig. 1. Longitudinal section from petiole of Masdevallia amabilis, x 450°. 

Fig. 2. Longitudinal section from petiole of Masdevallia Veitchiana, x 450°. 

Fig. 3. Epidermis bearing cone-shaped hairs from lateral sepals of Masdevallia amabilis, x 450°. 

Fig. 4. Epidermis bearing club-shaped hairs from lateral sepals of Masdevallia Chelsoni, x 450°. 

Fig. 5. Epidermis bearing spheroidal hairs from lateral sepals of Masdevallia Veitchiana, x 450°. 

Fig. 6. Vertical section of lower leaf surface from Rhododendron ciliatum, x 450°. The surface of each epi- 
dermal cell is slightly convex. 

Fig. 7. Similar section from Rhododendron Grievei, x 450°. The surface of each epidermal cell is enlarged 
into a conical process. 

Fig. 8. Similar section from Rhododendron glaucum, x 450°. The surface of each epidermal cell forms an 
evident papilla. 

Fig. 9. Vertical section of lower leaf surface from Rhododendron formosum, x 450°. 

Fig. 10. Similar section from Rhododendron formosum x R. Dalhousice, x 450°. 

Fig. 11. Similar section from Rhododendron Dalhousia?, x 450°. 

Fig. 12. Vertical section of lower leaf surface from Rhododendron Edgeworthii, x 450°. 

Fig. 13. Starch grains from rhizome cells of Hedycliium Gardnerianum, x 500°. 

Fig. 14. Grains from Hedycliium Sadlerianum, x 500°. 

Fig. 15. Grains from Hedychium coronarium, x 500°. 

Fig. 16. Grains from Hedychium elatum, x 500°. 

Fig. 17. Grains from Hedychium elatum x H. coronarium, x 500°. 



Plate VIII. 

Fig. 1. Transverse section, stem of Cytisus purpureus in second year of growth, x 150°. e., epidermis; eft, 

cortex ; s.s., sclerenchyma strand ; ph./., phloem fibres ; ph., phloem proper ; xy. 2 , xylem of 

second year ; xy. 1 , xylem of first year ; p., pith. 
Fig. 2. Transverse section, stem of Cytisus Adami, x 150°. Letters as above, c, cork, formed as an elliptic 

mass beneath the epidermis. 
Fig. 2a. Shows developing masses of cork (c.c), forming beneath the epidermis. 
Fig. 3. Transverse section, stem of Cytisus Laburnum, x 150°. Letters as above. 
Figs. 4 and 5. Upper and lower leaf epidermis of Cytisus purpureus, x 400°. 
Figs. 6 and 7. Upper and lower leaf epidermis of Cytisus Adami, x 400°. 
Figs. 8 and 9. Upper and lower leaf epidermis of Cytisus Laburnum, x 400°. 
Fig. 10. Epidermal cells of Cytisus purpureus, stained in watery eosin, x 1500°. The figure shows the average 

size of the cell nuclei. In one cell the protoplasm is represented. 
Fig. 11. Similar cells of Cytisus Adami, x 1500°. 
Fig. 1 2. Similar cells of Cytisus Laburnum, x 1 500°. 

Fig. 13, a, a', a". Standard, wing, and keel petal of Cytisus purpureus ; nat. size. 
Fig. 13, b, V, b". Standard, wing, and keel petal of Cytisus Adami; nat. size. 
Fig. 13, c, c', c". Standard, wing, and keel petal of Cytisus Laburnum ; nat. size. 
Fig. 14a. Pollen grains of Cytisus purpureus, x 350°. 

Fig. lib. Pollen grains of Cytisus Adami, x 350°. Two of these are abortive. 
Fig. 14c. Pollen grains of Cytisus Laburnum, x 350°. 




•4r 

3 MAY. 95 



Trans. Roy. Soc. Edm r , Vol. XXXVII 
DM.M.MACFARLANE ON "PLANT HYBRIDS" Plate 1. 




M'Fa.T]ane 4. Erskine. Lith™ Edin r 



Trans. Roy. Soc. Edm r , Vol. XXXVII. 
D r J.M.MACFARLANE ON "PLANT HYBRIDS" Plate II. 




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ROYAL SOCIETY OF EDINBURGH. 

VOL. XXXVII. PART II.— (Nos. 15 to 24)— FOR THE SESSION 1892-93. 



CONTENTS. 



PAGE 

XV. The Skull and Visceral Skeleton of the Greenland Shark, Laemargus tnicrocephalus. J'>y 
Philip J. White, M.B., Demonstrator of Zoology, University of Edinburgh. Communi- 
cated by Professor Ewakt. (With Two Plates), ...... 287 

XVI. (Jit, the Fossil Plants oj the Kilmarnock, Galston, and Kilwinning Coal Fields, Ayrshire. 

By Robert ivinsTox, F.R.S.E., F.G.S. (Plates I.-IV.), . .... 307 

XVII. Electrolytic Synthesis of Dibasic Acids. By Professor A. Csufi Brown and Dr James 
Walker. IT. On the Electrolysis of the Ethyl-Potassium Sail* of Saturated Dibasic 
Ar.ii/.-; with Side Chain*, and on Secondary Reactions accompanying the Electrolytic 
Synthesis of Dibasic Acids, . . . . . . . . - .'3G1 

XVII 1. On Imparl, II. By Professor Tait, . . . . . . .381 

XIX. A New Algebra, by means of whicJi Permutations ran be transformed in a variety of ways, 

and their properties investigated. By T. B. Sprague, M.A., F.R.S.E., . . . o!)t) 

XX. On the Particle* in Fogs and Cloud*. By John Aitkex, Esq., F.R.S., E.R.S.E., . . IP'S 

XXL On the Path of a Rotating Spherical Projectile. By Professor Tait. (With a Plate), . 427 

XXII. On the Pres< nt Slide of Knowledge and Opinion in regard to Colour-Blindness. By William 
Pole, F.R.S., F.R.S.E., Mus. Doe. Oxon., Honorary Secretary of the Institution of Civil 
Engineers. (With a Plate), ........ Ill 

XXI I I. On tfu Chemical Change* which take place in the Composition of theSea-Water associated 

ivith Blue Muds on the Floor of the Ocean. By John Murray, LL.D., Ph.D., and , 
Robert Irvine, F.C.S., ......... 181 

XXIV. Tin Anatomy and Relations of tlie Eurypterida. By Malcolm Laurie, B.Sc., B.A., E.L.S. 

Communicated by R. 11. Traquair, M.I)., F.R.S., F.R.S.E. (With Two Plates), . 509 




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MDCCCXCIII. 



(Issued November J. 189,3.) 



( 287 ) 



XV. — The Skull and Visceral Skeleton of the Greenland Shark, Lsemargus micro- 
cephalus. By Philip J. White, M.B., Demonstrator of Zoology, University of 
Edinburgh. Communicated by Professor Ewart. (With Two Plates.) 

(Read 15th July 1889.) 

Some time ago, at the request of Professor Ewart, I undertook an examination of 
the skull and visceral skeleton of the Greenland shark, Lsemargus microcephalus. This 
I readily consented to do, not only because no attempt had yet been made to describe 
these structures in this shark, but because they claim careful consideration in view of 
the recent work by Professor Ewart on the cranial nerves of Elasmobranchs. 

In this paper I shall endeavour, without entering into too much detail, to point out 
some of the more salient features of the skull and visceral skeleton of Lsemargus, and to 
compare them with those of other Elasmobranchs where that seems necessary. 

I have made preparations of the above-named structures from the heads of several 
specimens of Lsemargus. The sharks from which the heads were taken were of various 
sizes, the smallest being about six feet in length, and the largest twelve. As might have 
been expected, the skeletal parts of these heads are very similar to each other, but I have 
noticed among the few specimens I have examined points of difference, which make me 
wish I had a larger number of preparations at my disposal, to enable me to decide the 
more usual conditions. 

The Skull (Plate I.). 

Following the example of Gegenbaur, I shall, for purposes of description, speak of 
the skull as consisting of four regions, viz., the occipital, the auditory,* the orbital, and 
the ethmoidal regions. The occipital region, which is in part continuous with the 
vertebral column, lies behind the canals for the pneumogastric nerves ; the auditory 
extends from these canals forwards as far as the wide canals for the transmission of the 
trigeminal and other nerves ; the orbital region, situated in front of the auditory, may 
be said to lie between the post-orbital and pre-orbital processes ; the part of the skull in 
front of the orbital region forms the ethmoidal region. 



The Occipital Region. 

This region, which is small compared with the other cranial regions, is in part con- 
tinuous with the vertebral column, and lies, as above stated, behind the canals for the 

* Gegenbaur terms this — Labyrinth-Region. 
VOL. XXXVII. PART II. (NO. 15). 2 T 



288 MR PHILIP J. WHITE ON THE 

pneumogastric nerves. Owing to the oblique direction of these canals from within 
outwards and backwards, the region is marked out somewhat in the form of a V. The 
apex of this V is directed forwards, and its short backwardly-directed limbs receive the 
anterior portion of the first vertebra between them. The fore part of this vertebra, save 
at a point (Fig. 5, S3) on either side of its arch, is in contact with the occipital region. 
Mesially, its centrum (Figs. 3 and 5, V") is continuous with the skull, but the lateral 
portions of its centrum (Fig. 3, Vp), which present considerable expansions, are distinct 
therefrom, although firmly bound to it by connective tissue. These lateral vertebral 
expansions abut against the occipital processes (Op), which are thrown outwards 
and backwards from the occipital region. The surfaces of the vertebral expansions and 
occipital processes where they meet each other are smooth. Again, the anterior portion 
of the arch of the first vertebra (Fig. 5, V) lies within the occipital foramen, and is in 
contact with its upper and lateral margins. A canal (Fig. 5, S3) for the transmission of 
the third spinal nerve lies on either side between the skull and the middle portion of the 
vertebral arch. The part of the arch below these canals rests on slanting surfaces on 
the lower lateral edge of the foramen magnum, and the part above them enters more 
freely within the foramen, and is overlapped by its dorso-lateral margin. In the smaller 
skulls of Laemargus examined I find that the neural arch, although bound to the 
margin of the foramen magnum by connective tissue, is distinct from it, and this con- 
nection permits of a little movement in a vertical direction ; but in the largest skull 
at my disposal I noticed a much more intimate connection between the arch of the first 
vertebra and the skull. Especially is this the case with the portion of the arch below the 
canals for the third spinal nerves, where the arch and skull are continuous with each other. 

In its cranio-vertebral connection Laeinargus presents affinities to Hexanchus and 
such forms as Acanthias and Scymnus. In having the lower mesial portion of the first 
vertebra continuous with the cranium, and in having an intimate relation between the 
arch of this vertebra and the margin of the foramen magnum, Laemargus ranks with 
Hexanchus ; in the connection of the expanded portions of the first vertebral centrum 
with the occipital processes it agrees with Acanthias, Scymnus, &c. I find no joint 
cavities existing between the lateral vertebral expansions and the occipital processes. 
It appears that Gegenbaur finds such in Scymnus. 

The dorsal portion of the occipital region slopes backwards towards the vertebral 
column, and at its hinder part is somewhat vertical. In a line with the spinous processes 
of the vertebrae, and extending from the back of the parietal fossa (Figs. 1 and 5, P) on 
the roof of the skull to the foramen magnum, is a crest, the occipital crest (Co), which 
is most prominent about the middle of its extent. Its development in Laemargus 
resembles that found in Acanthias and Centrophorus calceus, rather than that of 
Hexanchus or Heptanchus, in the latter of which the crest attains its greatest develop- 
ment among Selachians. 

The ventral portion of the occipital region is continuous with, and assists in forming 
the hinder part of the large basilar plate (Fig. 3, Bp) of cartilage which constitutes 



SKULL AND VISCERAL SKELETON OF THE GREENLAND SHARK. 289 

the greater portion of the basal area for the posterior half of the skull. Sometimes the 
occipital part of this plate is irregular, and has processes standing out from it. 

Pneumogastric Canals. — The outer opening of each canal (Fig. 1, Yg f ) is large 
and funnel-shaped, and is placed at the back of the skull, external to an occipital 
process. Each canal pursues a course from within backwards and outwards. Beside 
each pneumogastric canal are two canals, with a similar direction, for the first and second 
spinal nerves, and their outer orifices are placed near each other, internal to the pneumo- 
gastric foramina. In the skulls in which I followed up these canals I noticed that in 
part of their course they communicated with the pneumogastric passage. 

Gegenbaur describes in Hexanchus and in other Selachians a canal, the orifice of 
which is situated on each postero-lateral edge of the auditory region, near the foramen of 
exit for the glosso-pharyngeal and pneumogastric nerves. These canals he describes 
with the occipital region, since each opens into a pneumogastric canal. A vein which 
he considers to be the primitive jugular vein passes along each of these canals. In 
Lsemargus I do not find this canal, but I notice that a vein which opens into the anterior 
cardinal sinus issues from the pneumogastric canal in company with the nerve. If this 
vein corresponds to that described by Gegenbaur as passing along a separate canal for 
part of its extent, it may be concluded that in Lsemargus this canal has blended with 
that for the pneumogastric nerve. 



The Auditory Region. 

This region is continuous with the occipital region behind, and with the orbital in 
front. The pneumogastric canals mark its limit behind, and at its fore part are the wide 
passages for transmitting the trigeminal and other nerves. The external configuration 
of this region is little affected by the organ of hearing which it contains, the semicircular 
canals and vestibules giving rise to no such elevations as are so characteristic of some 
Selachian skulls. 

The dorsal aspect of this region presents on either side a crest, internal to which is a 
shallow groove on which are several foramina. These lateral crests, which project 
outwards and upwards, commence in front in a small eminence, and are continued from 
this point backwards to the hinder part of the auditory region. The central part of 
the dorsal surface is slightly raised, and the parietal fossa (Figs. 1 and 5, P) is situated 
here. This fossa is deepest posteriorly, and in this position the vestibular aqueducts 
open. The floor of the fossa slopes gently upwards towards the surface of the skull, and 
its lateral edges becoming more prominent as they pass backwards, meet at its hinder 
part, in a small elevation (Pm). 

The ventral portion of the auditory region forms a considerable portion of the 
basilar plate (Fig. 3, Bp) of the skull. A groove (C^), for a carotid artery, beginning 
on each side about the anterior third of the lateral edge of this plate, runs forwards 



290 ME PHILJP J. WHITE ON THE 

and inwards to a carotid canal (Ca'). The grooves may be bridged over with cartilage 
in part of their extent. 

On the lateral surface of the auditory region, at its lower and hinder part, is the 
depression (Fig. 4, j f) which forms an articular surface for the two heads of the 
hyomandibular cartilage. The long axis of this depression is directed from above down- 
wards and backwards, and for the most part it is distinctly demarcated from the 
surrounding parts. It exhibits two surfaces, an upper and a lower, incompletely 
separated from each other. The upper joint surface (j) is smaller than the lower (/), 
and a small process, from which a distinct rim runs upwards and gradually fades away, 
is situated at its lower and anterior part. The larger articular surface is deep compared 
with the upper, and the basilar portion of the skull juts outwards under its lower part, 
while at its upper and hinder part a stout process stands out from the skull, and over- 
hangs it. 

In possessing a cranio-hyoid joint with two surfaces, the skull of Lsemargus agrees 
with Zygaena. 

A pyramidal process (Figs. 1, 3, and 4, Ap) projects backwards from the auditory 
region behind the cranio-hyoid joint. The lower surface of this process (Fig. 3) is 
flattened, but its upper (Fig. 1) presents two grooved surfaces, an internal and an ex- 
ternal, separated from each other by a ridge. The former of these leads up to the exit 
foramen ( Vg') for the vagus, and the latter (Gp') to that for the glosso-pharyngeal nerve. 

A groove, the post-orbital groove (Fig. 4, Pg), begins above the smaller articular 
surface of the cranio-hyoid joint, and is continued forwards and downwards to 
terminate at the inter-orbital foramen (Io'), which lies a short distance below 
the foramen (Tr'), for the trigeminal and other nerves. About the middle " of its 
course, the groove is bridged over by a band of cartilage (x). The space beneath this 
band, towards its fore part, is separated by a cartilaginous shelf into an upper and a 
lower chamber, the former of which lodges, in the recent state, part of the orbital 
sinus, while the latter contains part of the facial nerve, the palatine branch of which 
escapes in front (PI), while another portion of the nerve passes from beneath the 
band posteriorly. The lower part of the band may be perforated at several points for 
the passage of nerves. A ridge extends from about the middle of this band at its 
anterior part and forms the anterior and lower boundary of the post-orbital groove, and 
the upper border of a groove which lies below it. This second groove leads to a deep 
depression (y), at the bottom of which are two foramina. The hyoid artery rests in 
this groove, and the foramina, which are the orifices of canals opening internally on the 
lateral wall of the pituitary fossa, are for the branches of this artery. The band-like 
arrangement covering the exit foramen of part of the facial is interesting, as in 
Rhynchobatis, Trygon, Pristis, and Squatina a similar band covers the outer opening of 
the facial canal. 

Glosso-pharyngeal Canal. — The inner opening (Fig. 5, Gp) of this canal is placed 
at the lower and lateral part of the cranial cavity, in front of the pneumogastric 



SKULL AND VISCERAL SKELETON OF THE GREENLAND SHARK. 291 

foramen (Vg). From this point to its external orifice it pursues a course from within 
outwards and backwards, and passes through the cranial wall external to and at a lower 
level than the vagus canal. The canal in question is not continuous throughout, its 
continuity being broken a short distance after its commencement, as it here opens into 
the lower part of the vestibule of the ear. After a short interval, the canal is continued, 
and passes to its outer opening (Figs. 1 and 4, Gp'). The first part of the canal is 
narrow, the second is wide. In communicating with the vestibular part of the auditory 
capsule, and consisting of a narrow and a wide part, the glosso-pharyngeal canal of 
Lsemargus is similar to that of Centrophorus calceus, Acanthias, and the Eays. 

The Facial Canal. — This canal, which is short, commences just inside a depression 
(Fig. 5, Af), which is common to part of the facial and the auditory nerve, and passes 
transversely outwards, to open in the space under the band of cartilage, already men- 
tioned, on the lateral aspect of the auditory region. 

The Orbital Region. 

This region lies between the auditory region behind, and the ethmoidal in front. 
The post-orbital processes (Figs. 1, 3, and 4, Po), and the canals (Tr') for the trigeminal 
and other nerves mark its posterior boundary, while the pre-orbital processes (Pr) and 
ridges running downwards from them serve as its anterior limitation. A capacious 
orbital cavity lies on either side of this region, and the supra-orbital crests, with their 
post- and pre-orbital processes, stand boldly out from the skull. 

The dorsal portion of the orbital region (Fig. 1) forms the broadest part of the 
skull, and presents on each side a concavity between the pre- and post-orbital processes. 
Between the post-orbital processes there is a considerable median depression, in front 
of which are two smaller depressions also occupying the mid-dorsal line. Internal 
to each supra-orbital ridge there is a groove, the supra-orbital groove, continued for- 
wards from a groove occupying a similar position in the auditory region, and on 
the floor of this the supra-orbital foramina (&r) are situated. There are six or 
seven of these foramina on each side, and one of the hindermost of them is always 
larger than the others. In this respect Lsemargus agrees with Centrophorus calceus, 
Galeus, and Mustelus. The supra-orbital grooves are deepest anteriorly, and in this 
position each receives the upper opening of the pre-orbital canal (Pr"). Two 
grooves, one of which runs along the inner and dorsal part of the nasal capsule, 
while the other turns outwards and leads to the hinder part (em) of the ethmoidal canal, 
commence at the point where the pre-orbital canal opens. 

The ventral aspect (Fig. 3) of this region of the skull presents a comparatively 
narrow anterior and a broad posterior portion. The broad part forms the anterior 
portion of the basilar plate (Bp) of the skull, and in front, on each side, it throws out a 
shoulder-like process. In front of each shoulder is a concavity, the palato-basal 
depression (Pd), for lodging the palato-basal process (PI. II. Fig. 1, Pp) of the palato- 



292 MR PHILIP J. WHITE ON THE 

quadrate cartilage (ppt). The basal angle (Fig. 4, A) is not so marked in Lsemargus as 
in the Notidanidse or in Scymnus, but seems rather to resemble that of Acanthias. 
The narrower anterior basal portion of this region projects in the middle line, and forms 
the hinder part of a keel (K) which runs under the ethmoidal region. The outer 
openings (Co') of the carotid canals, which will subsequently be described, are placed 
towards the anterior part of the basilar plate. A small mesial aperture (He), which is 
the lower opening of a canal, evidently the hypophysis canal, is also found at the anterior 
part of the basilar plate. 

The orbital cavity (Fig. 4). — Each cavity is overhung by a supra-orbital ridge with 
its pre- and post-orbital processes. Its anterior boundary is formed by a cartilaginous 
ridge, which, curving downwards from the pre-orbital process, gives rise to an 
antorbital process (An) at the fore part of the orbit, and then curving backwards 
from this point fades away as it approaches the palato-basal depression (Pd). Behind, 
the orbital cavity has no distinct boundary as the auditory region merely slopes 
forwards and inwards towards the orbital basin. A sort of floor is formed to the 
orbital cavity behind by an outward projection of the basilar plate, but in front of this 
the orbit is devoid of a floor. 

The post-orbital process. — This process (Figs. 1, 3, and 4, Po), which is of con- 
siderable strength and size, is pyramidal in form, and has its apex directed outwards, 
downwards, and backwards. One surface is directed upwards, a second downwards 
and forwards, and a third downwards and backwards. The process resembles that found 
in Acanthias. 

The pre-orbital process (Figs. 1, 3, and 4, Pr). — This process, which is not so pro- 
minent as the post-orbital, is connected in front with the roof of the nasal capsule by a band 
of cartilage (b) which roofs in the ethmoidal canal. The base of the process is pierced 
by two canals, the upper and larger of which is the pre-orbital. The lower canal, which 
is also found in Scyllium and Galeus, opens on the roof of the skull just in front of the 
pre-orbital opening (Pr"). 

The palato-basal depressions (Figs. 3 and 4, Pol), the position of which has already 
been indicated, are distinctly seen, one on each side of the inter-orbital septum. They have 
a direction upwards and backwards, and a prominent ridge runs upwards from the 
shoulders of the basilar plate and forms a hinder boundary for them. In. front of the 
depressions there is a less pronounced ridge. 

Canal for the trigeminal and abducens nerves and the ophthalmic and buccal 
branches of the facial. — This is a large canal, and its external orifice (Fig. 4, T/) is 
situated at the back of the orbital cavity, considerably below the post-orbital process, 
and its position in Lsemargus corresponds with that in Scymnus. The canal is short and 
wide, and has a direction from within outwards and forwards. Its anterior wall is 
less extensive than its posterior. 

Caned for the oculi-motor nerve. — This canal passes almost directly outward through 
the cranial wall, and its outer opening (Fig. 4, Om') is placed a short distance in 



SKULL AND VISCERAL SKELETON OF THE GREENLAND SHARK. 293 

front of that for the trigeminal and other nerves. The part of the skull through which 
this canal runs is thick. 

Canal for the optic nerve. — This is a wide canal, and like the former passes almost 
directly outwards through the skull wall. In a side view of the skull its outer orifice 
(Fig. 4, 0') is seen lying considerably in front of that of the canal for the trigeminal and 
other nerves. 

Canal for the patheticus. — This is a narrow canal, having from within a direction 
outwards, downwards, and slightly forwards. Its outer opening (Fig. 4, Pa') is placed 
at the upper part of the orbital cavity, and lies either directly above the optic foramen 
or a little behind that point. 

Pre-orbital canal. — The hinder opening (Fig. 3, Pr') of this canal is situated at the 
anterior and upper part of the orbit. The canal pierces the base of the pre-orbital process, 
and runs from the orbital cavity to open (Fig. 1, Pr") on the roof of the cranium. A 
second canal, which has already been noted, lies below it. 

Orbito-nasal canal. — This canal, which has its hinder orifice (Fig. 3, On) some 
distance below that for the pre-orbital, passes forwards and slightly inwards, to open 
(On') on the surface of the skull at the hinder and inner part of the nasal capsule. 

Inter-orbital canal. — The outer aperture (Fig. 4, Io') of this canal, the course of 
which will be followed later, lies a little below the foramen of exit for the trigeminal 
and other nerves. 

The Eye-stalk (PL I. Fig. 3, E. ; PI. II. Fig. 5).— This is an elongated rod, con- 
tinuous at its proximal end (m) with the skull, and articulating at its distal extremity 
(m') with the cartilaginous sclerotic of the eye-ball (PI. II. Fig. 6). The stalk is slender 
at its proximal part, but increases in thickness towards its distal extremity, where it 
presents a somewhat triangular cupped surface on which, in the recent state, the eye-ball 
rests. The cartilage of which it is composed is similar to that composing the skull. 

The Ethmoidal Region. 

This region, which lies in front of the orbital, exhibits on either side the somewhat 
flattened nasal capsules (Figs. 1 and 2, N) which form its lateral expansions. These 
are separated from each other above by the deep pre-frontal fossa (Fig. 1, P/"), and below 
by the inter-nasal septum. In front of the pre-frontal fossa the fore part of the region 
is produced forwards as a truncated rostrum (Figs. 1-5, R). The long axes of the 
nasal capsules have a direction forwards and slightly inwards. The ventro-lateral opening 
of each capsule is situated anteriorly, and its margin, which is very irregular, supports a 
ring-like nasal cartilage (Figs. 2, 3, and 4, Na). The ethmoidal canal (Fig. 4, em') is 
found at the outer and lateral part of the dorsal surface of the capsule. A series of 
longitudinal ridges, with narrow grooves between them, pass forwards and gently out- 
wards on the upper aspect of the capsule. These ridges and grooves are especially 
marked on the outer half of the roof of the capsule, and the latter lead to small canals 
which open anteriorly near the free margin of the structure. 



294 MR PHILIP J. WHITE ON THE 

Nasal-ring -cartilage (Figs. 2, 3, and 4, Na). — This is an incomplete ring of carti- 
lage which surrounds the greater part of the nasal orifice. Externally it is in contact 
with the free margin of the nasal capsule, and the two ununited ends of the ring are 
directed inwards, the lower of these being very slender. Processes approach each other 
from opposite points of the ring and thus divide the nasal orifice into an inner and outer 
part, an arrangement which is not uncommon among Selachians. 

The pre-frontal fossa (Figs. 1 and 5, Tf). — This is an elongated deep fossa 
which lies between the nasal capsules, and assists in separating them from each other. 
The opening of the fossa on the roof of the cranium is somewhat elliptical, and its 
margins, which are irregular and sometimes perforated at parts, curve downwards and 
outwards to the upper surface of the nasal capsules, and terminate in front at the rostrum. 

The inter-nasal septum. — This septum separates the nasal capsules from each other 
below. It is produced in front as a short truncated rostrum (Figs. 1-5, E), which 
is broader in front than behind. The ventral portion of the septum is laterally 
compressed and forms a keel (K), which runs forwards towards the rostrum. This keel 
is especially prominent at its hinder part, and in this respect Lsemargus agrees with 
Scymnus and Acanthias. 

The nasal fossa (Fig. 3, N/). — This is a deep fossa on the ventral surface, and lies 
between the inner border of the posterior half of each nasal capsule and the inter-nasal 
septum. These fossae also occur in some other Elasmobranchs. A canal which com- 
municates with the cranial cavity opens at the bottom of each fossa at its hinder part. 
A similar canal occurs in Heptanchus and some other forms, but not in Hexanchus. The 
presence of this canal, together with other evidence, gives a clue to the origin of the three- 
shanked rostrum found in some Selachians. A cartilaginous process (Fig. 3, P'), which may 
be loosely connected with the nasal capsule, projects inwards and backwards under each 
nasal fossa, and near the hinder part of the base of the process is the orifice (On") of a 
canal which runs upwards and forwards to open into the hinder part of the nasal cavity. 
The anterior opening of the orbito-nasal passage (On') lies a short distance behind the 
posterior opening of the canal just noted, and a short groove leads from one to the other. 



Vertical longitudinal Section of the Skull in the mesial plane (Fig. 5). 

This section shows, — the continuation of the cartilage of the first vertebral centrum 
with the skull, the thickness of the cranial roof and floor, the extent of the cranial 
cavity, as well as that of the parietal and pre-frontal fossae. 

The cranial cavity. — This cavity, which is considerably larger than the brain which it 
encloses, is open behind towards the neural canal, and is incompletely shut off from 
the pre-frontal fossa (P/) by a cartilaginous partition (D) in front. On each side 
this partition the cavity communicates with the nasal cavities through an olfactory 
passage. 



SKULL AND VISCERAL SKELETON OF THE GREENLAND SHARK. 295 

For descriptive purposes the cranial cavity may be described as consisting of a posterior, 
middle, and anterior division. The posterior portion extends from the foramen magnum 
to the hinder wall (Ds) of the pituitary fossa ; the middle from this point forwards to the 
optic foramina (0) ; and the anterior division lies in front of these openings. 

The posterior division. — This extends, as just stated, from the foramen magnum to the 
hinder wall or dorsum sella? (Ds) of the pituitary fossa. In some sharks, e.g. Hex- 
anchus, the dorsum sella? forms a considerable elevation on the cranial floor. Between 
this elevation and the foramen magnum there is a hollow, but in Lsemargus, as the dorsum 
sella? rises very slightly on the floor of the cavity, the hollow between it and the foramen 
magnum is very shallow. A distinct elevation passes from the dorsum sella? for a short 
distance up the cranial wall, and behind it the large foramen (Tr) for the trigeminal, 
abducens, and part of the facial nerve is situated, while the foramen (Om) for the oculi- 
motor, which belongs, however, to the middle cranial region, is placed in front of it. 
There is a depression (Af) a short distance behind the foramen for the trigeminal and 
other nerves, at the bottom of which are two foramina, an anterior for the portion of the 
facial nerve which does not pass through the trigeminal canal, and a posterior for the 
auditory nerve. The foramen (Grp) for the glosso-pharyngeal nerve is situated some 
distance behind the depression common to the two nerves just mentioned. The pneumo- 
gastric foramen (Vg), which has a funnel-shaped depression leading up to it, is situated 
behind that for the glosso-pharyngeal, but at a higher level. A small foramen (Si) for 
the first spinal nerve lies below the pneumogastric opening, that for the second spinal 
(S2), which is larger, is placed behind it, while the third spinal nerve passes through a 
canal (S3) situated between the skull and the arch of the first vertebra. In having 
apertures and canals for the first and second spinal nerves in the cranial wall, La?margus 
agrees with Scymnus, Acanthias, and some other sharks. 

A downward projection from the roof of the cavity, caused by the sinking of the floor 
of the parietal fossa (P), presents itself in this part of the cranium. From this projection 
the roof passes forwards and upwards to its highest elevation. 

The middle division. — This extends from the dorsum sella? (Ds) as far as the optic 
foramina (0), and its vertical diameter is greater than that of the division behind 
or before it. 

The pituitary fossa. — This fossa occupies the floor of the division, and extends from 
the dorsum sella? (Ds) to (M) its interior limit. The hinder part of the fossa is deep, 
and its anterior wall slopes upwards and forwards and terminates in the slight sinking 
(M) on the cranial floor. The hinder and postero-lateral walls of the fossa are especially 
steep. Several canals open at various points on the walls of the fossa. 

The carotid canals. — These two canals begin (Fig. 3, Qa'), as already seen, at the 
inner ends of the grooves (Cg) on the under surface of the basilar plate of the skull, and 
pass through the cranial floor, and meet each other a short distance behind the pituitary 
fossa. From their point of union a short wide canal passes forwards and slightly upwards 
to open (Fig. 5, Ca) on the hinder wall of the fossa at its lower part. 

VOL. XXXVII. PART II. (NO. 15). 2 U 



296 MR PHILIP J. WHITE ON THE 

A small shelf of cartilage (Io), with a transverse groove on its upper surface, lies 
over the carotid opening, and at either end of the groove the inner opening of the 
inter-orbital canal is placed. In the position of the shelf, the continuity of the 
inter-orbital canal as a cartilaginous tube is broken above, a condition which is found 
in Hexanchus and some other sharks. The portion of the canal on each side of the 
pituitary fossa, in Lsemargus, pursues from without, a curved course inwards and 
slightly forwards. 

The Hypophysis canal. — The internal opening of this canal (He), already alluded 
to, and which is presumably the persistent hypophysis canal, is seen on the anterior 
wall of the pituitary fossa. The canal has an oblique course passing upwards and back- 
wards from below. In one skull which I examined the canal had a vertical direction, and 
passed directly upwards to open at the lowest part of the fossa. Hexanchus and Hep- 
tanchus seem to have a canal which, while not so complete as in Lsemargus, apparently 
represents it in these forms. 

Two openings, a dorsal and a ventral, for the branches of the hyoid artery, are placed 
some distance apart on the postero-lateral walls of the fossa. 

The foramen (Qm)for the oculi-motor nerve, as already indicated, lies at the forepart 
of an elevation which passes outwards and upwards from the dorsum sellse. 

The optic foramen (0) is situated in a line with, but considerably in front of, that 
for the oculi-motor nerve. 

The patheticus foramen (Pa). — This is placed on the dorso-lateral wall of the cranial 
cavity, some distance above the optic foramen, and slightly posterior to it. 

The anterior division. — This division of the cranial cavity lies in front of the optic 
foramina. It is incompletely shut off from the pre-frontal fossa (P/*) by the cartilaginous 
partition (D), and on either side of this partition the cavity is produced as a wide 
olfactory passage. Each olfactory passage, although it is wide throughout, becomes 
narrower as it passes forwards and outwards to open at the hinder part of the nasal 
cavity. A foramen (z) for a blood-vessel is placed at the dorso-lateral part of this 
cranial division, near the commencement of the olfactory passage. 

The partition (D), which incompletely separates the cranial cavity from the pre- 
frontal fossa (P/), rises vertically from the cranial floor. In the skull figured, the partition 
is only connected at its lower part with the cranium by means of a narrow neck of 
cartilage, and as it does not touch the cranium at any other part, a space exists between 
it and the cranial wall, by means of which the cranial cavity and pre-frontal fossa 
communicate freely with each other. In another skull, the partition had three connec- 
tions with the cranium. There was a broad connection at its base with the cranial floor, 
and its upper part was connected with the cranial roof by two narrow bands of 
cartilage, one on either side. In this case, therefore, instead of a single space existing 
between the cranial cavity and pre-frontal fossa, there were three, — one dorsal, and one 
on either side. In a third skull, the largest cranium which I examined, not only 
was there an extensive basal continuation of the partition with the cranial floor, but 



SKULL AND VISCERAL SKELETON OF THE GREENLAND SHARK. 297 

the dorso-lateral connections were also extensive, and they largely encroached on the 
dorsal and lateral spaces, reducing them to wide canals. 

In other Elasmobranchs, a membranous partition stretches across the space between 
the cranial cavity and the pre-frontal fossa. 

The pre-frontal fossa (Pf). — This is an elongated deep fossa, which, as already 
mentioned, is open above (Fig. 1), and communicates with the cranial cavity posteriorly. 
It is deeper behind than in front, its floor slopes upwards to the rostrum, and towards 
its upper part its margins curve inwards towards each other. 

The parietal fossa (P). — This fossa has already been noticed (Figs. 1 and 5). In a 
longitudinal section of the skull, the opening of a vestibular aqueduct is seen posteriorly 
at the side of the floor of the fossa. 

The Notochord (C). — In Lsemargus, as in some other sharks, the notochord is 
persistent in the cranial floor. It passes forwards from the vertebral column to the 
vicinity of the pituitary fossa, and approaching the dorsum sellse, curves rather abruptly 
upwards. Its anterior extremity in some cases is directed forwards, in others it 
curves backwards, but in all cases it terminates just below the perichondrium of the 
cranial floor. The direction of the cranial notochord of Lsemargus bears a greater 
resemblance to that of Hexanchus or Heptanchus, than to that of such forms as 
Acanthias or Centrophorus calceus. 

The Visceral Skeleton (Plates I. and II.). 

The visceral skeleton consists (1) of the usual segmented hoops or arches, placed in 
succession one behind the other, and (2) of cartilages standing in relation to these. Of 
these arches there are seven. The first is the mandibular, the second the hyoid, and 
the remaining five are the branchial arches. 

The Branchial Arches (PI. I. Figs. 1 and 2, PI. II. Figs. 2 and 3). — These arches 
gradually decrease in size from before backwards. A typical arch, e.g. the third 
(PI. II. Fig. 2), consists on each side of the four segments which are usually 
found in Selachians. From above downwards, they are as follows, — (1) pharyngo- 
branchial (P&3), (2) epi-branchial (E3), (3) cerato-branchial (Kr3), and (4) hypo- 
branchial (H3). A series of cartilages, the basi-branchials (PL II. Fig. 3, B1-B8), 
occupy a mid-ventral position between the lower ends of the lateral portions of the 
arches. 

In several preparations of the visceral skeleton of Lsemargus which I have examined, 
I found the typical number of segments in the first four arches, while in other preparations 
I noticed that only the first, third, and fourth arches possess the typical number, the 
hypo-branchials of the second arch having fused together to form a single transversely 
placed plate of cartilage (PI. II. Fig. 3, H2). In some cases there is an intermediate 
condition in which this cartilaginous plate is incompletely divided. 

In all my dissections I found that the fifth arch possessed only two segments on each 



298 MR PHILIP J. WHITE ON THE 

side, namely, an epi- and a cerato-branchial segment, the former of which has its upper 
extremity fused with the pharyngo-branchial of the fourth arch. 

The pharyngo-branchials. — These are somewhat flattened rods, having their inner 
extremities free, and directed backwards and inwards (PI. I. Fig. 1, P&1-4), while their 
outer extremities are thickened, and are connected with the upper ends of the epi- 
branchials (E1-E5). The upper surfaces of the pharyngo-branchials present grooves 
(PI. II. Fig. 2, B(/3) on which, in the recent state, the efferent branchial vessels rest. 
In the first three arches the grooves have a direction from before, backwards and inwards, 
while the grooves on the fourth pair of pharyngo-branchials have an almost transverse 
direction from without inwards. The position of these grooves varies in the different 
pairs of pharyngo-branchials. On the first pair the grooves lie over the outer extremities 
of the cartilages, but in the case of the other arches they become more internal in position 
and gradually deeper from before backwards. In Squatina there is a farther modification, 
because here, instead of grooves, we find canals perforating the pharyngo-branchials of the 
second, third, and fourth arches. 

Each pharyngo-branchial of the fourth arch possesses a process (PI. II. Fig. 3, P5) 
which, springing from about the middle of its hinder border, and having a direction 
outwards and slightly downwards, is continuous with the epi-branchial of the fifth 
arch. This process is regarded by some as the pharyngo-branchial of the fifth 
branchial arch. This process is absent in Hexanchus, and in Heptanchus it is only 
slightly developed. Gegenbaur concludes from this that the process is developed from the 
pharyngo-branchial of the fourth arch, in order that a point of attachment may be given 
to the epi-branchial of the last arch, and that, therefore, it is not the representative of a 
pharyngo-branchial. In Lsemargus, as I have already mentioned, this process and 
the epi-branchial of the fifth arch are fused together, a condition which occurs in other 
Elasmobranchs. 

The epi-branchials (PI. II. Figs. 2 and 3, E1-E5). — There are five pairs of these, 
and from the first to the fourth they diminish in size. The fifth epi-branchial of either 
side (E5), together with the pharyngo-branchial processes (P5) of the fourth arch, forms 
an elongated rod. The upper extremities of the four anterior epi-branchials are movably 
connected with the outer extremities of the pharyngo-branchials, while the fifth, as 
already seen, forms a cartilaginous union with the fifth pharyngo-branchial. The lower 
extremities of all are movably connected with the upper ends of the cerato-branchials. 
Processes jut forwards from the upper extremities of the epi-branchials, and fossae, which 
increase in depth from behind forwards, are found on the inner surfaces of the four 
anterior cartilages. 

The cerato-branchials (PI. II. Figs. 2 and 3, Krl-Kr5). — These are the longest seg- 
ments in the branchial arches, and have their upper ends connected with the epi- 
branchials, but their lower extremities have various connections. The lower extremity of 
the cerato-branchial of the first gill arch, has lying in front of it, the small hypo-branchial 
(Fig. 3, Hi) belonging to this arch, and it also touches the basal portion of the 



SKULL AND VISCERAL SKELETON OF THE GREENLAND SHARK. 299 

hyoid arch, to which it is bound by connective tissue. The lower extremities of the 
cerato-branchials of the second, third, and fourth arches are connected with hypo- 
branchials (H2, H3, H4) respectively, while those of the fifth pair (Kr5), which differ 
considerably from those of the other arches, are bound, one on either side, to a large basi- 
branchial plate (B5). 

Processes project forwards from the lower ends of all the cerato-branchials, but those 
of the first arch are very feebly developed. Each process on the second, third, fourth, 
and fifth arches overlaps the portion of the cerato-branchial lying in front of it. Fossae, 
for muscular attachments, similar to those on the inner faces of the epi-branchials, are 
also found in corresponding positions on the first four cerato-branchials, close to their 
upper extremities. 

Hypo-hranchials (PI. II. Figs. 2 and 3, H1-H4). — There are four pairs of these 
cartilages, and they stand in relation to the first four branchial arches. The first pair 
(Hi) are very small cartilages, lying, as is already mentioned, at the fore part of the 
lower extremities of the cerato-branchials of the first gill arch, to which, in the recent 
state, they are bound on the one hand, and on the other to the hyoid arch, by connective 
tissue. In some sharks, e.g. Hexanchus, these pair of hypo-branchials are absent. The 
second pair of hypo-branchials (H2) may be fused together, as in Scymnus, and form a 
transversely placed plate of cartilage which lies between the lower ends of the cerato- 
branchials of the second gill arch. A process projects backwards from this plate, and in 
some cases a small process projects forwards from the middle of its anterior border. In 
other cases the anterior border of this plate presents a straight edge, as is shown in Plate 
II. Fig. 3. In several preparations I found this plate consisting of two symmetrical pieces. 

The third and fourth pairs of hypo-branchials (H3, H4), which have a slightly back- 
ward direction, much resemble each other. Their outer extremities are connected with 
cerato-branchials and their inner with basi-branchial cartilages. 

Basi-branchial cartilages (PI. I. Fig. 2, PI. II. Figs. 2 and 3, Bl-8). — These are a series 
of cartilages differing from each other in shape and size, varying slightly in number, and 
forming a broken line in the mid-ventral position. I found in most of the specimens of 
Lsemargus which I examined a larger number of these cartilages than have been described 
in any other Elasmobranch. Heptanchus has five of these, but Lsemargus has a number 
ranging from six to eight. The first basi-branchial (Bl), when present, is a small nodule 
of cartilage which lies in the interval between the basi-hyal cartilage (Bh) and the hypo- 
branchial plate (H2) of the first gill arch. Cestracion, so far as I am aware, is the only 
other Elasmobranch yet described which has a basi-branchial in this position. In two 
cases in which this cartilage was absent in Lsemargus, I noticed that the hypo-branchial 
plate (H2) of the first gill arch had a process projecting forwards from the centre of its 
anterior border, This is interesting, as there may be a possibility that in these cases, 
the first basi-branchial is fused with the hypo-branchial plate. In some cases, however, 
I found that the first basi-branchial was altogether absent, and the hypo-branchial plate 
presented a straight anterior edge. The second basi-branchial cartilage (B2) is placed 



300 MR PHILIP J. WHITE ON THE 

behind the hypo-branchial plate of the second gill arch, and is fastened to it in this posi- 
tion. The third basi-branchial (B3), which is followed by the fourth basi-branchial (B4), 
lies immediately behind the second. The fourth is larger than the two which precede it. 
The second and third basi-branchials lie between the inner extremities of the third pair 
of hypo-branchials, and the fourth basi-branchial assists in separating the inner ends of 
the fourth pair. Behind the fourth basi-branchial, but separated from it by a short 
interval, is the large expanded breast-plate-shaped basi-branchial cartilage (B5), which is 
the fifth of the basi-branchial series. It is broad anteriorly, but becomes narrower as it 
passes backwards. The fourth pair of hypo-branchials (H4) are, on the one hand, con- 
nected with the fourth basi-branchial (B4), and on the other, with the anterior edge of 
the fifth, and their inner ends, as they pass from one basi-branchial to the other, close 
in a space which exists between them. The cerato-branchials (Kr5) of the fifth gill 
arch are bound to the lateral edges of the fifth basi-branchial by connective tissue. The 
fifth basi-branchial is followed by three, it may be by two pieces of cartilage (B6, B7, B8), 
which are the sixth, seventh, and eighth basi-branchials. Narrow cartilages placed 
superficially are generally seen lying across the lines of contact of the fifth and sixth and 
the sixth and seventh basi-branchials. 

The Gill rays (PI. II. Figs. 2 and 4, ~Ry, ~Ry', R,y", R,y f "). — These are found in connec- 
tion with all the branchial arches, and are for the most part elongated rods, but in some 
places are represented by mere nodules of cartilage. In the four anterior branchial 
arches the rays are connected with the epi-branchial and cerato-branchial segments, but 
most of the rays belong to the latter. The number of the rays in the various arches 
is small as compared with that of some other Elasmobranchs. In Laemargus I 
found eight rays to be the average number for either side of the first gill arch, and 
five to be that for either side of the fourth. One of the rays at or near the middle 
of each series is larger than the others, and may be known as the central ray (%'). 
The gill rays of the fifth gill arch are much modified (Fig. 4). On the under surface 
of each cerato-branchial (Kr5) of this arch there is an elongated piece of cartilage (Ry") 
which is firmly bound to it, and at the outer end of this elongated cartilage I have 
found in several cases, but not all, small nodules of cartilage (Ry" r ), which, as Gegenbaur 
has pointed out, occur in some other Elasmobranchs, and are to be regarded as modified 
branchial rays. 

Extra-branchial cartilages (PI. I. Figs. 1 and 2, PI. II. Fig. 2, Ev", Ei/").—¥vom 
their position Gegenbaur calls these the outer gill arches. There are, counting those 
belonging to the hyoid arch, five pairs on each side of the middle line, forming a dorsal 
and ventral series. They belong to the hyoid arch and first four branchial arches. 
The extra-branchials are elongated rods of cartilage, expanded at their inner ends and 
with their outer extremities pointed. Most of the gill rays are directed towards them 
(PI. II. Fig. 2), and each of the upper extra-branchials is generally touched by one or 
more of them, but it is seldom that any ray reaches a lower extra- branchial. The outer 
end of each central branchial ray (Ry') lies midway between the outer extremities of a 



SKULL AND VISCERAL SKELETON OF THE GREENLAND SHARK. 301 

dorsal and a ventral extra-branchial. The extra-branchials lie for the most part posterior 
to the arches to which they belong. 

The gill rakers. — These, for the most part, are pointed or blunt processes of cartilage, 
lying chiefly on the inner surfaces of the cerato-branchials. Their bases rest on, and in 
some cases are continuous in this position with the cartilage of the arch to which they 
belong. Their free extremities project into the buccal cavity. 

The Hyoid Arch (PI. I. Figs. 1 and 2, PI. II. Fig. 3). 

This is a massive arch, and consists of a mesial and two lateral portions. Each of 
the lateral portions of the arch consists of the usual cartilaginous segments — an upper 
or hyo-mandibular (Hm), and a lower or cerato-hyal (Kh). The hyo- mandibular cartilage 
is short and broad, and when the parts are in apposition, stands out horizontally 
from the skull. The inner extremity of the cartilage presents an oblique surface with 
two heads (g,g f ) which are separated from each other by a shallow groove. The 
heads, of which the posterior is the larger, articulate with the two surfaces which 
exist in the cranio-hyoid depression of the skull (PI. I. Fig. 4, j,f). At the outer 
extremity of the hyo-mandibular, a strong process, which may be called the suspensorial 
process, projects forwards towards a similar process arising from the hinder part of the 
lower jaw. The two processes are connected by a ligament, in which a cartilage 
corresponding to an interarticular cartilage is imbedded. Some other sharks also possess 
a cartilage in this position. There is a depression on the lower surface of the suspensorial 
process, for articulating with the upper extremity of the cerato-hyal. 

Cerato-hyal (Kh). — This is an elongated curved bar of cartilage, and has a direction 
from without downwards, forwards, and inwards. A rounded prominence, which articulates 
with the depression on the under surface of the suspensorial process of the hyo-mandib- 
ular, rises from its upper extremity. The lower extremity of the cerato-hyal passes below 
the outer part of the basi-hyal (Bh), and rests in a depression which is there situated. 

Basi-hyal (Bh). — This is a block-like cartilage which lies between the lower ends of the 
cerato-hyals. Its anterior border is convex and its posterior is concave ; its dorsal surface 
is flattened, while its ventral presents a concavity. Postero-laterally, it is produced into 
two cornua, to which the lower extremities of the cerato-branchial cartilages of the first 
gill arch are bound by connective tissue. The first pair of hypo-branchials (Hi) lie at 
the hinder part of the cerato-basi-hyal joints, and they are also bound by connective 
tissue to the cartilages forming these joints. 

Hypo-hyal (Hh). — A nodule of cartilage is situated at the fore and upper part of 
each cerato-basi-hyal joint.* The cartilage occupies a position similar to that which the 
hypo-branchial (Hi) of the first gill arch does in front of the first cerato-branchial 
cartilage. It does not appear that these nodules have been noticed before in any other 
shark. They are evidently hypo-hyal cartilages. 

* These cartilages were absent in two of the sharks. 



302 MR PHILIP J. WHITE ON THE 

Hyoidgill rays. — These are either simple or branching rods of cartilage which project 
backwards and outwards from the hinder parts of the hyo-mandibular and cerato-hyal 
cartilages. As a rule, there are about eleven rays on each side, the majority of the rays 
springing from the cerato-hyal. The ray on either side of the joint, formed by the hyo- 
mandibular and cerato-hyal cartilages, is stouter than the others. 

Extra-branchials. — There are two of these on each side, an upper and a lower, and 
they form the first of the series of extra-branchial cartilages (PI. I. Figs. 1 and 2, Ev, Ev'). 
None of the hyoid gill rays touch the upper extra-branchials of this arch, but several are 
in contact with each of the lower extra-branchials. 

The Mandibular Arch. 

This consists of the palato-pterygoid and mandibular cartilages which constitute the 
upper and lower jaws (PL I. Figs. 1 and 2, PI. II. Fig. l). 

The Upper Jaw. — This is formed by the two palato-pterygoid cartilages (Ppt), one 
on each side of the middle line. The anterior extremities of these cartilages are bound 
together by ligament, but they do not touch one another, while their posterior ends are 
widely separated. Each cartilage has a direction from before backwards and outwards. 
Immediately external to the maxillary symphysis there is a slight elevation of the carti- 
lage, to the outer side of which lies the narrowest portion of the palato-quadrate. 
The elevation just noted is much more marked in Scymnus. Beyond its narrowest 
portion the palato-pterygoid becomes suddenly wide, and continues so to its posterior 
extremity. At the commencement of the wide portion a large somewhat conical process, 
the palato-basal process (Pp), is placed on the upper part of the jaw. In the recent state 
this process rests on the palato-basal depression (PI. I. Fig. 4, Fd) of the skull. At the 
inner part of the base of the process there is a deep hollow, above which there is a con- 
siderable projection. Each palato-basal process is surmounted by a nodule of cartilage (n). 
The upper edge of the palato-pterygoid behind the palato-basal process becomes much 
everted, and the upper part of the inner surface of the cartilage, especially towards its 
hinder part, looks upwards and backwards. The outer surface of the palato-pterygoid 
in its posterior two-thirds presents a concavity. At the posterior extremity of the cartilage 
there is a faceted surface internally and an articular process externally, both of which 
are for articulating with the lower jaw. 

Teeth are found on the lower and inner part of the anterior two-thirds of the palato- 
pterygoid cartilage. The younger teeth lie in a depression which is bounded above by a 
ridge. 

The Pre-spiracular Cartilages (PI. I. Fig. 1, Ps). — These are two small flattened 
cartilages which rest on the surfaces of the palato-pterygoid cartilages, which are directed 
upwards and backwards. The cartilages are longer than they are broad, and have a direc- 
tion upwards, forwards, and outwards. 

TJie Lower Jaw. — The lower, like the upper, jaw consists of two cartilages, the man- 
dibular cartilages (Mm), one on either side of the mesial plane, and are bound together in 






SKULL AND VISCERAL SKELETON OF THE GREENLAND SHARK. 303 

front, but widely separated behind. The anterior ends of the cartilages are only in con- 
tact with each other for a short distance, and below this point of contact an elliptical 
piece of cartilage, the basi-mandibular (PL I. Fig. 2, Bm), lies between them. The 
mandibular cartilages, which are wide at the symphysis, increase in width as they pass out- 
wards and backwards. Internally, at the hinder part of each cartilage, a rounded process 
projects backwards and inwards. In the recent state, a ligament, in which an interarti- 
cular cartilage lies imbedded, connects this with the suspensorial process of the cerato- 
hyal cartilage. On the upper surface of the rounded process just described there is an 
articular process which abuts against a similar surface on the upper jaw. External to 
the process there is a concavity on which the articular process at the posterior end of 
the palato-pterygoid rests. 

Teeth are found along the upper edge and inner surface of each mandibular cartilage 
in its anterior two-thirds. A narrow shelf of cartilage lies along the lower part of the 
dentigerous surface, and above this shelf the youngest teeth are situated. 

Labial Cartilages (PL I. Fig. 2, PL II. Fig. 1, L 1/ L"). — These stand in relation to 
the upper and lower jaws. There are three cartilages on each side, and of the three, two 
(L I/) stand in relation to a palato-pterygoid cartilage, while the third (L") lies in relation 
to a mandibular cartilage. The two upper cartilages lie across the palato- quadrate cartilage 
about the middle of its extent. One of them (L/) is an elongated, curved, cylindrical rod, 
which has a direction from above downwards and backwards, and its lower extremity is 
connected with a similar rod of cartilage (L") which is connected with the mandibular 
cartilage. The other upper labial cartilage (L), which is flattened, is shorter than the 
one just described, and lies across its upper extremity, and is superficial to it. The labial 
(L") of the lower mandibular cartilage resembles the rod-like cartilage of the palato- 
pterygoid. It has a direction from below upwards and backwards. Its upper extremity 
is bound to the upper rod-like cartilage by connective tissue, and the two meet each other 
at the angle of the mouth. 

The Cartilage of the Skull and Visceral Skeleton. 

The cartilage of which these are composed is soft as in Hexanchus, and yields readily 
to the scalpel. Only in a few parts does it show any indication of becoming calcified. 

Points of Special Interest 

The points which I consider of special interest in the skull and visceral skeleton are 
the following: — (1) the cranio-vertebral connection; (2) the presence of an hypophysis 
canal ; (3) the presence of a basi-mandibular cartilage ; (4) the presence of a hypo-hyal 
cartilage at the fore and upper part of each cerato-basi-hyal joint ; (5) the large 
number of basi-branchial cartilages, Laemargus possessing more of these than are found 
in any other Elasmobranch yet described ; (6) the soft nature of the cartilage of the 
cranium and visceral skeleton. 

VOL. XXXVII. PART II. (NO. 15). 2 X 



o04 MR PHILIP J. WHITE ON THE 



LITERATURE CONSULTED. 

Dr Carl Gegenbaur. Untersuchungen zur Vergleichenden Anatomie der Wirbelthiere. Das Kopfskelet der 
Selachier, ah Grundlage zur Beurtheilung der Genese des Kopfskeletes der Wirbelthiere, 1872. 

Dr H. G. Eronn's Klassen und Ordnungen des Thier-reichs. "Der Schadel." — "Das Visceralskelet." 1876. 

W. K. Parker, F.R.S. On the Structure and Development of the Skull in Sharks and Skates. Transactions 
of the Zoological Society of London, 1879. 

T. Jeffery Parker. A Course of Instruction in Zootomy. "The Skate." 1884. 

Marshall and Hurst. Practical Zoology. " The Dog-fish." 1888. 



INDEX TO PLATES. 



Plate I. 

Fig. 1. Dorsal view of the skull and visceral skeleton. 

Fig. 2. Ventral view of the skull and visceral skeleton. 

Fig. 3. Ventral view of the skull. 

Fig. 4. Side view of the skull. 

Fig. 5. Vertical longitudinal section of the skull in the mesial plane. 

Plate II. 
Fig. 1. Upper and lower jaws. 
Fig. 2. Portion of the third branchial arch. 
Fig. 3. Hyoid and branchial arches laid out. 

Fig. 4. Cerato-branchial of the fifth branchial arch and rudimentary gill rays. 
Fig. 5. Eye-stalk. 
Fig. 6. Cartilaginous sclerotic. 

Note. — All the figures, with the exception of Figs. 4, 5, and 6, PI. II., which are natural size, are one- 
third of the natural size. 

Figs. 5 and 6, PI. II., are from a shark twelve feet long, and all the other figures are taken from specimens 
from six to seven feet in length. 
A. Basal angle. 

A/. Foramen common to facial and auditory nerves. 
An. Antorbital process. 
Ap. Auditory process. 
Bl-8. Basi-branchial cartilages. 

h. Strap of cartilage covering ethmoidal canal. 
B^/3, Br/4. Grooves on third and fourth pharyngo-branchial cartilages. 
B/i. Basi-hyal cartilage. 
Bm. Basi-mandibular cartilage. 
Bp. Basilar plate. 

C. Notochord. 
Ca. Inner opening of carotid canal. 
Ca'. Outer opening of carotid canal. 
C'/. Carotid groove. 
Co. Occipital crest. 



SKULL AND VISCERAL SKELETON OF THE GREENLAND SHARK. 305 

D. Cartilaginous partition (incomplete) between cranial cavity and pre-frontal fossa. 
Ds. Dorsum sellae. 

E. Eye-stalk. 

El-5. Epi-branchial cartilages. 

e. Cut extremity of eye-stalk on skull. 
em. Ethmoidal foramen (upper). 
em'. Ethmoidal foramen (lower). 
E/', Ew', Ew", Ew'". Extra-branchial cartilages. 

F. Prominence at hinder part of sclerotic for articulating with cup of eye stalk. 
g, g'. Heads of hyo-mandibular cartilage. 

Op. Glosso-pharyngeal foramen (inner). 
Op'. Glosso-pharyngeal foramen (outer). 
Hl-4. Hypo-branchial cartilages. 
He. Hypophysis canal. 
H/i. Hypo-hyal cartilage. 
Hm. Hyomandibular cartilage. 

lo. Inner opening of inter-orbital canal. 

Io'. Outer opening of inter-orbital canal. 

J. Point of articulation of upper and lower jaws. 
j,f. Cranio-hyoid depression. 

K. Keel at lower part of internasal septum. 
KA. Cerato-hyal cartilage. 
Krl-5. Cerato-branehial cartilages. 
L L' L". Labial cartilages. 

M. Anterior limit of pituitary fossa. 

to. Proximal (cut) extremity of eye-stalk. 

to'. Distal extremity of eye-stalk. 
Mra. Lower jaw. 

N. Nasal capsule. 

n. Nodule of cartilage surmounting palato-basal process. 
Na. Nasal-ring cartilage. 
N/. Nasal fossa. 

0. Optic foramen (inner). 

O'. Optic foramen (outer). 

O". Optic foramen in sclerotic. 
Ora. Oculi-motor foramen (inner). 
Om'. Oculi-motor foramen (outer). 

On. Posterior opening of orbito-nasal canal. 
On'. Anterior opening of orbito-nasal canal. 
On". Orifice of canal in front of orbito-nasal canal. 

Op. Occipital process. 
P. Parietal fossa. 

P'. Cartilaginous process underlying nasal fossa. 

Pa. Patheticus foramen (inner). 

Pa'. Patheticus foramen (outer). 

Pol-5. Pharyngo-branchial cartilages. 

Po\ Palato-basal depression. 

P/. Pre-frontal fossa. 

Pa. Post-orbital groove. 

VI. Foramen of exit for palatine branch of facial nerve. 
Pto. Parietal eminence. 

Po. Post-orbital process. 

Pp. Palato-basal process. 



306 MR PHILIP J. WHITE ON THE GREENLAND SHARK. 

Vpt. Palato-pterygoid cartilage. 
Pr. Pre-orbital process. 
Pr". Pre-orbital foramen (upper). 
P?*'. Pre-orbital foramen (lower). 
Ps. Pre-spiracular cartilage. 
R. Rostrum. 
R//, Ky', R//", R//'". Branchial rays. 

SI, S2, S3. Foramina for 1st, 2nd, and 3rd spinal nerves. 
Sr. Supra-orbital foramina. 

Tr. Foramen (inner) for trigeminal and abducens nerves and part of facial complex. 
Tr'. Foramen (outer) for trigeminal and abducens nerves and part of facial complex. 
V. Vertebral column. 
V. Arch of first vertebra. 
Y". Centrum of first vertebra. 
Yg. Pneumogastric foramen (inner). 
Yg'. Pneumogastric foramen (outer). 
Yp. Lateral expansion of centrum of first vertebra. 
X. Strap of cartilage covering facial canal. 
Y. Foramen for hyoid artery. 
Z. Foramen for blood-vessel. 



Tra-ns. Roy. Soc. Edm r , Vol. XXXVII. 
M r P J.White on the Greenland Shark p LATE I. 




MTatlane k Erslune, LicW, Edin T 



J 



Trans. Roy. Soc. Edm r Vol. XXXVII 
M r P. J.White on the Greenland Shark Plate II. 




It/Sc^ 



\ • J 



307 



XVI. — On the Fossil Plants of the Kilmarnock, Galston, and Kilwinning Coal Fields, 
Ayrshire. By Kobert Kidston, F.K.S.E., F.G.S. (Plates I.-IV.) 

(Read 1st June 1891.) 

Introduction. 

The tract of land embraced in the area from which the fossils have been derived, that 
form the subject of the present Memoir, extends in an easterly direction from Saltcoats 
to Newmilns, a distance of about 19 miles. At both extremities, the Coal Measures 
narrow down to under half a mile wide at Saltcoats, and about a mile broad at New- 
milns. The greatest width is found towards the centre of the field, where in a north- 
east and south-west direction it is over 12 miles broad. 

The whole of the Coal Measures occurring in Ayrshire are referable to the Lower 
Coal Measures. The Lower Coal Measures contain, however, two well-marked groups : — 

I. An Upper Series of red and purple sandstones and clays, barren of coals. 
II. A Lower Series consisting of grey, white, and yellow sandstones, dark shales, 
fireclays, coal seams and ironstones. 

These two series of the Lower Coal Measures of Scotland are almost invariably 
referred to by local geologists as the Upper and Lower Coal Measures. The terms 
so used are not only misleading, but are inaccurate when applied to the Coal Measures 
as developed in Britain. If we regard the British Coal Measures as a whole, and 
in no other way can they be considered, if any satisfactory classification is to be 
adopted, then the whole of the Scotch Coal Measures must be termed Lower Coal 
Measures.* 

The Upper, Middle, and Lower Coal Measures are well developed in different parts 
of England, and as typical localities where these may be seen, the following may be 
mentioned : — 

Upper Coal Measures. — Radstock Coal Field, Somerset. 

Middle Coal Measures. — South Staffordshire Coal Field (Dudley), and part of the 
Yorkshire Coal Field. 

Lower Coal Measures. — Part of the Yorkshire and Northumberland Coal Fields. 
In the Coal Field of the Potteries, North Staffordshire, the three divisions of the 
Coal Measures are present. 

One cannot insist too strongly on the absolute necessity of using definite and the 

* Perhaps certain beds in Fife may form an exception to this general statement, but that district requires further 
investigation. 

VOL. XXXVII. PART II. (NO. 16). 2 Y 



308 MR "ROBERT KIDSTON ON THE FOSSIL PLANTS OF THE 

same terms, for the same rocks, whether occurring in England or Scotland; and the 
loose manner in which the terms Upper and Lower Coal Measures are used by some 
sxeolojnsts has led to needless confusion in the correlation of the British Coal Measures. 
On the other hand, it is most desirable that the two series of the Lower Coal Measures 
should be clearly distinguished, but this is easily done by adopting the terms Upper 
and Lower Series to the two groups composing our Lower Coal Measures, and I hope 
that local geologists will adopt these or similar terms, and entirely give up the misleading 
designations of Upper and Lower Coal Measures when speaking of the two series of the 
Scotch Lower Coal Measures. 

All the species recorded in this paper (with the exception of Stigmaria stettata) are 
from the Lower Series of the Lower Coal Measures. 

There are two chief centres of mining operations in this portion of the Ayrshire Coal 
Measures, generally known as the Kilmarnock and Galston and the Kilwinning Coal Fields. 
These two districts form part of the same coal field, and many of the seams are common 
to both areas, though frequently going under different names, the names having been 
given before the seams were correlated. 

As usually found in all coal fields, and even in those of limited extent, certain seams 
workable at one point split up and become too thin to work, or entirely die out, in another 
part of the same coal field, and such cases are seen here. 

I give five vertical sections from different parts of the coal field, which show the 
position of the principal coal seams, and from which can also be learnt the general 
structure of the district, and the principal names that have been applied to the various 
coal seams (see Table). 

The section of No. 1 pit, Windyedge, Kilmarnock, has been given me by Mr Hugh 
S. Dunn, jr., Kilmarnock. 

The general section of the Kilwinning Coal Field has been prepared by Mr J. Smith, 
Kilwinning. 

The Annandale Colliery section has been communicated by Mr J. Rorrison, Springhill. 

The section of strata in No. 6 pit, Bonnyton Colliery, near Kilmarnock, was procured 
for me by Mr A. Sinclair, Riccarton. 

The section of No. 1 pit, Grange, was kindly supplied to me by Mr Yates, and in 
the letter from Mr Geo. H. Geddes which accompanied it, it is stated that no regular 
journal was kept during the sinking of the pit, which explains the term used, " mixed 
strata." 

The great thickness of boulder clay and of sand and gravel are a peculiar feature in 
this pit, as well as the red sandstone above the coals. Mr Geddes further states, that 
he is not sure that it is correct to say that the whole of the 300 feet of red sandstone 
and faikes, lying between the sand and gravel, is one bed of sandstone with faikes in the 
lower part of it ; but in any case, the sandstone bed is of great thickness. 

The sand and gravel and this red sandstone were the cause of much expense in sinking 
through them on account of the water they gave off. 



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KILMARNOCK, GALSTON, AND KILWINNING COAL FIELDS, AYRSHIRE. 309 

In looking over the horizons from which the fossils contained in the following list 
have been collected, one cannot fail to be struck with the absence of all records of fossil 
plants from some of the coal seams. The explanation is, that the shales overlying some 
of the coals are very barren, and though I have no doubt that more careful observations 
would have revealed some plant remains, still fossils are, in the cases referred to, very rare, 
and when they do occur, are probably so imperfect and fragmentary that specimens have 
not been collected. Mr Smith informed me that the only specimen of fossil plant that 
he ever saw from the turf coal at Kilwinning, was the single example of Sigillaria 
Walchii, Sauveur, which forms our only record for the species. 

The Whistler Seam, Kilmarnock, appears to be the most fossiliferous, and from it have 
been collected the greater portion of the species known to occur in the district. Future 
investigations may show that some of the species are more common than we at present 
suspect, and I hope that no opportunity will be lost in increasing our knowledge of the 
fossil flora of this coal field. 

The Kilmarnock and Kilwinning Coal Fields afford many fine sections for studying 
the strata. The sandstone quarries of Stevenston, Dean Quarry, near Kilmarnock, and 
Woodhill Quarry, Kilmaurs, gave interesting sections, where, in addition to good exposures 
of the bedded sandstones, one or more coal seams were seen. The two former are not 
worked at present, and being partially filled with water, some of their interest is lost ; 
but that at Woodhill, Kilmaurs, which is still worked, exhibits the following section : — 

Boulder clay (not shown in woodcut) — 

a. Grey sandy shale with nodules of impure clay ironstone. (This is 

the bed which has yielded many good fossil remains), . 5 feet. 

b. White sandstone, . . . . . 15 or 16 feet. 

c. Soft grey shale, ...... 3 feet. 

d. Durroch coal, ...... 2 feet. 

e. Dark shale with Stigmaria and spores,* . . .2 inches. 

Curious balls of coal occur in some of the seams. They vary in size from very small 
to larger than a man's head. In composition they do not differ 
from the rest of the seam, and the ordinary bedding of the 
coal passes through them. It is difficult to explain how they 
have been formed. Mr Smith, who has sent me a small specimen 
from the lower part of the Parrot Coal of Kilwinning, is of 
opinion, that in that case at all events, it is the result of heat, 
and this may possibly be the explanation. I have also speci- 
mens from the Tourha' Coal, Bonnyton Pit, Kilmarnock. The 

lf . Tin -r» Tf • i • t Section exposed at Woodhill 

coal lormmg the balls at Bonnyton Pit is equal in quality to the Quarry. 

rest of the seam. As the result of burning, some of the coal at Muirkirk has assumed 

a columnar structure. 

* I am indebted to Mr A. Sinclair for this section. 




310 MR ROBERT KIDSTON ON THE FOSSIL PLANTS OF THE 

The material on which the present communication is founded, is the result of full) 7 
ten years collecting on the part of many local geologists, who have given special atten- 
tion to the subject, and to these gentlemen I take this opportunity of offering them my 
best thanks for all the assistance they have so willingly and kindly given me, whilst 
working up the Fossil Flora of the district, and I specially wish to mention Mr J. Smith, 
Kilwinning ; Mr J. Rorrison, Springhill ; Mr D. Beverdige, Annandale Colliery, near 
Kilmarnock ; Mr A. Sinclair, Riccarton ; Messrs J. Stevenson, T. Steel, J. Gilchrist, 
W. Hillhouse, and J. M'Mirren, Kilmarnock; and Mr R. Linton, Kilmaurs ; but 
above all am I indebted to the Rev. D. Landsborough, Kilmarnock, who has taken 
the deepest interest in the matter, and kept up a constant communication amongst the 
workers on my behalf.* 

I have given a full list of references, and the synonymy of the species included in the 
following pages. 

Synopsis of Species. 

(From the Lower Series of the Lower Coal Measures.) 

Calamarieae. 

Calamites, Suckow. 

Group I. — C alamitina, Weiss. 

Calamitina varians, Stemb., var. insignis, Weiss. 

Calamites (Calamitina) varians, var. insignis, Weiss, Steinkohlen Calamarien, part ii. pp. 62, 63, pi. i., 

and pi. xxviii. fig. 1. 
Calamites varians, Germar, Vers, von Wettin u. Lobejun, Heft iv. p. 47, pi. xx. 
Calamites varians, Schenk., Richthofen's Cliina, vol. iv. p. 234, pi. xxxv. fig. 5 (? pi. xxxiv. fig. 1), 1883. 

Remarks. — A single specimen of this plant has been collected, and, though it only 
shows a small portion of a stem, I have no hesitation in referring it to Weiss' Calamitina 
varians, var. insignis. 

Locality. — Woodhill Quarry, Kilmaurs. 
Horizon. — Shale over Sandstone.t 

Calamitina Gopperti, Ett., sp. 

Calamites Gopperti, Ett., Steinkf. v. Radnitz, p. 27, pi. i. figs. 3, 4. 
Calamitina Gopperti, "Weiss, Steinkohlen Calamarien, part i. p. 127, pi. xvii. figs. 1, 2. 
Calamitina (Calamites) Gopperti, Kidston, Trans. York. Nat. Union, part xiv. p. 16, 1890. 
Calamophyllites Goepperti, Zeillcr, Flore foss. d. bassin houil. d. Valenciennes, p. 363, pi. lviii. fig. 1. 
Calamites (Calamitina) varians abbreviatus, Weiss, Steinkohlen Calamarien, part ii. pp. 62 and 73, pi. 
xvia. figs. 10, 11. 

* Publications of the Geological Survey of Scotland relating to the Galston, Kilmarnock, and Kilwinning Coal 
Fields : — Geological Map, sheet 22. Memoirs. Ayrshire (north part), with parts of Renfrewshire and Lanarkshire, 
Explanation of sheet 22, 1872. Horizontal Sections, sheet 5. Vertical Sections, sheet 3. 

t This is about 18 feet above the Durroch Coal. 



KILMARNOCK, GALSTON, AND KILWINNING COAL FIELDS, AYRSHIRE. 31] 

Catamites (Calamitina) varians inconstans,Weiss, ifo"c?.,vol.ii.pp. B2 and 69, pi. xvia. figs. 7, 8; pi. xxv. fig. 2. 
Calamites {Calamitina) varians inconstans, Kidston, Trans. Roy. Soc. Edin., vol. xxxv. part ii. p. 388, 
pi. i. fig. 1. 
(?) Calamites vertieillatus, Williamson (not L and H.), Phil. Trans., 1874, p. 66, pi. vii. fig. 45. 
Cyclocladia major, Feistmantel (in part), Vers. d. b'olim. Ablager, part i. p. 96, pi. i. fig. 8. 

Locality. — No. 3 Pit, Springhill, Crosshouse, near Kilmarnock. 
Horizon. — Shale over Major Coal. 

Calamitina verticillata, L. and H., sp. 

(Plate IV. fig. 18.) 

Calamites vertieillatus, L. and H., Fossil Flora, vol. ii. p. 159, pi. exxxix. 

Calamitina verticillata, Kidston, Trans. York. Nat. Union, part xiv., 1890, p. 17. 

Calamophyllites vertieillatus, Zeiller, Flore foss. d. bassin houil. d. Valenciennes, p. 360, pi. lvii. fig. 2. 

Description: — Branch scars periodic, oblong-quadrate, approximate laterally, cicatrice 
of scar slightly below the middle, outer surface of bark feebly ribbed ; the ribs almost 
Hat, with a very slight dividing furrow ; leaf-scars rounded- quadrate, catenulate. 

Remarks. — This species, described by Lindley and Htjtton from Hound Hill, near 
Pontefract, Yorkshire (Middle Coal Measures), is very rare in Britain, the example figured 
being the only specimen I have yet seen. The branch-scars are oblong-quadrate, and 
from the point of attachment of the appendicular organ there extend a few radiating 
ridges. Although I use the term " branch -scars" to these discs, it is quite possible that 
they bore cones ; but on this point there is no data. The flat ribs do not alternate 
regularly. At the nodes many of them continue straight on, to the opposite side of the 
leaf-scar, and they are seen to continue over the large discs where the pressure of the 
base of the attached organ has not been sufficient to obliterate them. The bark is still 
preserved on the specimen. The discs are formed by the pressure of the base of the 
appendicular branch or organ on the back, which was attached to the almost central cicatrice. 

Zeiller notes this species from Anzin in the north of France. 

I do not think that the plant figured by Ettingshausen as Calamites vertieillatus 
can possibly be referred to this species.* 

The Kilmarnock specimen was communicated to me by Mr Eorrison. 

Locality. — No. 3 Pit, Springhill, Crosshouse. 
Horizon. — Shale over Major Coal. 

Calamitina approximata, Brongt., sp. (in part). 
(Plate II. figs. 5, 6.) 

Calamites approximatus, Brongt. {in part), Hist. d. veget. foss., p. 133, pi. xxiv. figs. 2, 3 (? figs. 4, 5). 
Calamites approximatus, Geinitz (in part), Vers. d. Steinlcf. in Sachsen, p. 7, pi. xi. fig. 5 ; pi. xii. fig. 3. 
Calamitina approximata, Weiss, ISteirikolilen Calamarien, part ii. p. 81, pi. xxv. fig 1. 

* Haidinger's Naturwissensch., vol. iv. Abth. i., 1851, p. 68, pi. viii. fig. 1 



312 MR ROBERT KIDSTON ON THE FOSSIL PLANTS OF THE 

Description. — Internodes vefy short, arched ; large scars periodic, distant ; ribs 
prominent, with deep dividing furrows, generally continuous, much more rarely alter- 
nating at the nodes, and running together at the branch-scars. Envelope surrounding 
pit cavity of considerable thickness. 

Remarks. — Under this name have frequently been figured plants belonging to more 
than one species. Brongniart himself seems to have included two species under it. 
His figures 7, 8, pi. xv., and fig. 1, pi. xxiv., appear to be specifically distinct from the 
plants figured on pi. xxiv. figs. 2, 3. These latter I regard as the true Catamites 
approximata, and the former are probably to be referred to the Catamites Schiitzei, 
Stur.* The Catamites approximatus, L. and H.,t is to be referred to Catamites 
cruciatus, var. senarius, Weiss, \ and their Catamites approximatus, vol. i. pi. lxxvii., 
probably to C. Schiitzei, Stur. To this last species should, perhaps, also be referred the 
Catamites approximatus, Artis.§ 

Very little is known about the true characters of this species, the only specimens yet 
discovered being merely casts of the pith cavity, from which the above imperfect descrip- 
tion is drawn up. Of the two specimens figured, that on Plate II. fig. 5, at the point 
marked with the a, indicates the position of one of the verticils of branch-scars ; below 
it are fifteen internodes without any trace of another verticil of branch-scars. In the 
fine specimen figured by Weiss (toe. cit.) the internodes between the verticils of large scars 
are seven to eight. On the other specimen, figured on Plate II. fig. 6, there are nineteen 
very short internodes, on none of which are any traces of branch-scars. On fig. 5, 
between the line indicated at b, is a carbonaceous staining on the stone, which indicates 
the thickness of the vascular elements, or of both vascular tissues and bark, the 
distinction of the parts not being possible in the present condition of the fossil. The 
fossil shows, however, that the pith cavity, represented by its cast (which has often 
erroneously been supposed to represent the complete stem), was surrounded by a thick 
envelope. The two specimens of Caiamitina approximata which I figure, and which 
are two of only a small number of specimens seen from Ayrshire, show, as has 
already been observed in the case of Catamitina verticiltata, that, as a rule, the ribs 
do not alternate at the nodes. This is also seen on the figure given by Weiss, to 
which I have already referred. In this character they show some approach to the 
genus Asterocatamites. I do not give any measurements in the descriptions, as 
the specimens are photographed natural size, and in minor details measurements 
vary on different specimens, though the characters given in the description seem to 
be constant. 

The two specimens figured have been communicated to me by the Rev. D. 
Landsborough. 

* Sitzungsb. der k. Alcad. der Wiss., 1 Abth. vol. lxxxiii., 1881, p. 416, pi. i. fig. 1. 

t Fossil Flora, vol. ii. pi. ccxvi. 

} See Trans. Roy. Soc. Edin., vol. xxxiii. p. 340, fig. 1. 

§ Antediluvian Phytology, pi. iv: 



KILMARNOCK, GALSTON, AND KILWINNING COAL FIELDS, AYRSHIRE. 313 

Locality. — Woodhill Quarry, Kilmaurs. 

Horizon. — Shale over Sandstone. 
Locality. — Stevenston. 

Horizon. — Eoof of "f Coal." 



Group II. — E ucalamites, Weiss. 
Calamites ramosus, Artis. 

Calamites ramosus, Artis, Antedil. Phyt, pi. ii. 

Calamites ramosus, Brongt., Hist. d. veget. foss., p. 127, pi. xvii. figs. 5, 6. 

Calamites ramosus, Weiss, Aus. d. SteinJwhl., p. 10, pi. viii. fig. 44, 1882. 

Calamites ramosus, Kidston, Trans. Geol. Soc. Glasgow, vol. viii. p. 51, pi. iii. fig. 1. 

Calamites ramosus, Stur (in part), Calamarien d. Carb. Flora d. Schatz. Schichlen, p. 96, pi. xii. figs. 

1-4 (not 5, 6) ; pi. xii6. figs. 1-4 (5 ?), 6 ; pi. xiii. figs. 1-9 ; pi. xiv. figs. 3-5. Text figures — 

1, p. 4 ; 2 (?), p. 8 ; 31, p. 104 ; 32, p. 105. 
Calamites (Eucalamites) ramostts, Weiss, Steinkohlen Calamarien, part ii. p. 98, pi. ii. fig. 3 ; pi. v. figs. 

1, 2 ; pi. vi. ; pi. vii. figs. 1, 2 ; pi. viii. figs. 1, 2, 4 ; pi. ix. figs. 1, 2 ; pi. x. fig. 1 ; pi. xx. 

figs. 1, 2. (Includes Annularia ramosa and Calamostachtjs ramosa.) 
Calamites ramosus, Sauveur, Veget. foss. d. terr. houil. Belgique, pi. ix. figs. 2, 3. 
Calamites ramosus, Zeiller, Flore foss. d. bassin houil. d. Valen., p. 345, pi. lv. fig. 3 ; pi. lvi. fig. 3. 
Calamites nodosus, L. and H. (in part ; not Schlotheim), vol. i. pi. xv. (pars). 
Calamites nodosus, Lebour, Illustrations of Fossil Plants, pp. 3 and 7, pis. ii. iii. 
Calamites nodosus, Sternb. (not Schlotheim), Ess. fl. monde prim., i. fasc. 2, pp. 30 and 36, pi. xvii. fig. 2 ; 

fasc. 4, p. xxvii. 
Calamites carinatus, Sternb., ibid., i. fasc. 3, pp. 40 and 44, pi. xxxii. fig. 1 ; fasc. 4, p. xxvii. 
Calamites communis, Ett. (in part), Steinkf. v. Radnitz, p. 24, pi. iii. fig. 2 ; pi. iv. fig. 4. 

Foliage : — 

Asterophyllites radiatus, Brongt., Class, d. veget. foss., p. 35, pi. vi. figs, la, 7b. 

Annularia radiata, Brongt., Prod., p. 156. 

Annularia radiata, Feistmantel, Vers. d. bbhm. Kohlenab., p. 130, pi. xvii. figs. 2-4. 

Annidaria radiata, Renault, Cours d. botan. foss., vol. ii. p. 133, pi. xx. fig. 4, 1882. 

Annularia radiata, Roehl, Foss. Flora d. Steink. Form. Westph., p. 28, pi. iv. fig. 3 (?4). 

Annularia radiata, Sauveur, Veget. foss. d. terr. houil. Belgique., pi. lxvii. fig. 2. 

Annularia radiata, Zeiller., Veget. foss. du terr. houil., p. 24, pi. clx. fig. 1. 

Annularia radiata, Zeiller., Flore foss. d. bassin houil. d. Valen., p. 394, pi. lix. fig. 8; pi. lxi. figs. 1, 2. 

Asterophyllites foliosa, Feistmantel, Vers. d. bbhm. Kohlenab., p. 121 (? pi. xiv. figs. 2, 3, 4). 

Asterophyllites foliosa, Geinitz (in part), Vers. d. Steinkf. in Sachsen, p. 10, pi. xvi. figs. 2, 3 (not figs. 1 

and 4). 
Asterophyllites foliosa, L. andH., Fossil Flora, vol. i. pi. xxv. 

Annularia minida, Ettingshausen, Haidinger's Naturwiss. Abhandl., vol. iv. Abth. i. p. 83, pi. x. figs. 1, 2. 
Annularia asterophylloides, Sauveur, Veget. foss. d. terr. houil. cle la Belgique, pi. lxvii. fig. 1. 
Asterophyllites patens, Sauveur, ibid., pi. lxix. fig. 4. 
Annularia patens, Kidston, Trans. Geol. Soc. Glasgow, vol. viii. p. 53, pi. iii. fig. 2. 

Remarks. — Calamites ramosus is a common coal-measure fossil, occurring in the 
Upper, Middle, and Lower Coal Measures, though most plentifully in the two last 
divisions. 



314 MR ROBERT KIDSTON ON THE FOSSIL PLANTS OF THE 

The right-hand branch on Lindley and Hutton's plate xv., as well as their plate 
xvi., does not belong to Calamites ramosus, Artis (= Catamites nodosus, L. and EL). 
These figures, which have so long done duty as the foliage of this Catamite, have been 
found on more careful examination to be spikes of cones, whose position in regard to the 
stem on plate xv. is merely accidental. This supposed foliage of Catamites ramosus is 
really a spike of cones referable to the genus Pala&ostachya, whereas the cones of Cata- 
mites ramosus, which have been described by Weiss (toe. cit. ), belong to the Calamostachys 
type of cone. 

Locality. — No. 3, Springhill Pit, Crosshouse. 

Horizon. — Shale above Major Coal. 
Localities. — Bed of Irvine Water, near Kilmarnock, and Bonnyton Pit, Kilmarnock. 

Horizon. — Shale above Whistler Coal. 
Locality. — Woodhill Quarry, Kilmaurs. 

Horizon. — Shale over Sandstone. 
Locality. — No. 3 Pit, Springhill, near Dreghorn. 

Horizon. — Near " Lin Bed." 
Locality. — Galston. 
Horizon. — (?) 



Group III. — S tylocalamites, Weiss. 
Calamites Suckowii, Brongt. 

Calamites Suckowii, Brongt., Hist. d. veget. foss., p. 124 (pi. xiv. fig. 6?), pi. xv. figs. 1-6; pi. xvi. (fig. 1 1) 

figs. 2, 3, 4. 
Calamites Suckowii, Weiss, Foss. Flora d.jiingst. Stk. u. Both., p. 117, pi. xiii. fig. 5. 
Calamites Suckowii, Weiss, Steinkohlen Calamarien, part i. p. 123, pi. xix. fig. 1, 1876; part ii. p. 129, 

pi. ii. fig. 1 ; pi. iii. figs. 2, 3; pi. iv. fig. 1; pi. xxvii. fig. 3, 1884. 
Calamites Suckoicii, Feistmantel (in part), Vers. d. bohm. Kohlenab., Abth. i. p. 102, pi. ii. figs. 3, 4 ; pi. 

iii. figs. 1, 2 ; pi. iv. figs. 1, 2; pi. v.; pi. vi. fig. 1. (Excl. as fruit H. carinata.) 
Calamites Suckowii, Roehl, Foss. Flora d. Steink.-Form. Westph., p. 9, pi. i. fig. 6; pi. ii. fig. 2. 
Calamites Suckowii, Zeiller, Veget. foss. d. terr. houil., p. 12, pi. clix. fig. 1. 
Calamites Suckoicii, Zeiller, Flore foss. d. bassin. houil. d. Valen., p. 333, pi. liv. figs. 2, 3; pi. Iv. 

fig. 1. 
Calamites Suckoicii, Geinitz, Vers. d. Steinkf. in Sachsen, p. 6, pi. xiii. figs. 1, 3, 5, 6 (41). 
Calamites Suckowii, Gutbier, Vers. d. Zwick. Schicarzkohl , p. 17, pi. ii. fig. 1 (not fig. 2). 
Calamites Suckowii, Sauvcur, Veget. foss. d. terr. houil. Belgique, pi. iii., pi. iv. figs. 1, 2 ; pi. xi. fig. 3. 
Calamites Suckowii, Grand' Eury, Flore Carbon, d. Depart, de la Loire, p. 14, pi. i. figs. 1-6. 
Calamites Suckowii, Stur (in part), Calamarien d. Carbon. Flora d. Schatz. Schiclit., p. 145, pi. iii. fig*. 

3, 4; pi. v. figs. 5, 6 (not pis. i. fig. 3, ix. fig. 2, xiv. fig. 1). 
Calamites decoratus, Artis, Anted.il. Phyt., pi. xxiv. 

Calamites decoratus, Brongt. (inpart), Hist. d. ve'gdt. foss., p. 123, pi. xiv. figs. 1, 2 (not figs. 3, 4). 
Calamites Steinhaueri , Brongt., ibid., p. 135, pi. xviii. fig. 4. 

Phytolitlms sulcatus, Steinhauer, Trans. Amer. Phil. Soc, 1818, p. 277, pi. v. figs. 1, 2. 
Calamites Artisii, Sauveur, Veget. foss. d. terr. houil. Belgique, pi. vii. figs. 1, 2. 



KILMARNOCK, GALSTON, AND KILWINNING COAL FIELDS, AYRSHIRE. 315 

Catamites nodosus, Sauveur (not Schloth.), ibid., pi. xii. fig. 3. 

Catamites — Base of a stem, L. and H., Fossil Flora, vol. ii. pi. xcvi. 

Catamites approximates, Feistmantel (not Brongt.), Vers. d. bbhm. Koldenab., Abth. i. pi. vii. fig. 1. 

Catamites cannceformis, Lebour (not Schloth.), pi. i. 

Catamites cannceformis, L. and H. (not Schloth.), vol. i. pi. lxxix. 

Catamites irregularis, Achepohl, Niederrhein. Westfal. Steinkohlen, p. 89, pi. xxviii. fig. 2. 

Remarks. — A very common and widely distributed species, which occurs in all the 
divisions of the Coal Measures. 

I believe that Calamites Steinhaueri, Brongt. (= Phytolithus sulcatus, Steinhauer), 
is only founded on a large basal portion of Calamites Suchowii. Except in size, there is 
nothing to distinguish it. 

Locality. — No. 3 Pit, Springhill, Crosshouse. 

Horizon. — Shale over Major Coal. 
Localities. — Bonnyton Pit, Kilmarnock, and Dean, Kilmarnock Water. 

Horizon. — Shale above Whistler Coal. 
Locality. — No. 10 Pit, Annandale Colliery, Kilmarnock. 

Horizon. — Eoof of Splint Coal. 
Locality. — Woodhill Quarry, Kilmaurs. 

Horizon. — Shale over Sandstone. 
Locality. — Hurlford, near Kilmarnock. 

Horizon. — ? 
Locality. — Windyedge, near Crosshouse. 

Horizon. — Shale near Annandale Main Coal. 



Calamites undulatus, Sternb. 

Catamites undulatus, Sternb., Ess. fl. monde prim., i. fasc. 4, p. xxvi.; ii. fasc. 5, 6, p. 47, pi. i. fig. 2 

(1 pi. xx. fig. 8). 
Calamites undulatus, Brongt., Hist. d. veget. foss., p. 127, pi. xvii. figs. 1-4. 
Calamites undulatus, Zeiller, Flore foss. d. bassin houil. d. Valenciennes, p. 338, pi. liv. figs. 1, 4. 
Calamites undulatus, Sauveur, Veget. foss. d. terr. houil. de la Belgique, pi. v. figs. 1-3; pi. viii. fig. 1. 
Catamites undulatus, Seward, Geol. Mag., Dec. iii. vol. v. p. 289, pi. ix. 1888. 
Calamites undidatus, Kidston, Trans. York. Nat. Union, part xiv. p. 21, 1889. 
Catamites undulatus, Dawson, Fossil Plants Low. Carb. and Millstone Grit Form. Canada, p. 30, pi. viii. 

figs. 66-68 (?figs. 69-73). 
Catamites (Stylocalamites) Suchowii, var. undulatus, Weiss, Steinkohlen Calamarien, part ii. pp. 129, 134, 

135, pi. xvii. fig. 4. 
Calamites decoratus, Brongt., Class, d. veget. foss., pp. 17, 89, pi. i. fig. 1. 

Calamites decoratus, Brongt. (in part), Hist. d. veget. foss., p. 123, pi. xiv. figs. 3, 4 (not figs. 1, 2). 
Calamites cannaiformis, Roehl (not Schlotheim), Floss. Fora d. Steink.-Form. Westphdlens, p. 12, pL ii. 

% 3. 
Calamites inosquus, Achepohl, Neiderrhein. Westfal. Steinkohl., p. 114, pi. xxxiv. fig. 15, 1883. 
Calamites duplex, Achepohl, ibid., p. 135, pi. xli. fig. 11. 

VOL. XXXVII. PART II. (NO. 16). 2 Z 



316 MR ROBERT KIDSTON ON THE FOSSIL PLANTS OF THE 

Remarks. — This species is much less common in the Lower Coal Measures than Cata- 
mites Suchoiuii, Brongt., or Catamites ramosus, Artis. 
Locality. — Boimyton Pit, Kilmarnock. 

Horizon. — Shale over Whistler Seam. 
Locality. — Grange Pit, Kilmarnock. 

Horizon. — Shale over " Stranger " Seam. 
Locality. — No. 16 Pit, Woodhill Colliery, Kilmaurs. 

Horizon. — Eoof of Splint Coal. 

Calamites Cistii, Brongt. 

Catamites Cistii, Brongt., Hist. d. vdgdt. foss., p. 129, pi. xx. 

Calamites Cistii, Zeiller, Flore foss. d. bassin Jwuil. d. Valen., p. 342, pi. lvi. figs. 1, 2. 

Calamites Cistii, Grand' Eury, Flore Carb. d. Depart, de la Loire, p. 19, pi. ii. figs. 2, 3 (1 fig. 1). 

Calamites Cistii, Geinitz, Vers. d. Steinkf. in Sachsen, p. 7 (? pi. xi. figs. 7, 8 ; pi. xii. figs. 4, 5 ; pi. xiii. 

fig. 7). 
Calamites Cistii, Heer, Flora foss. Helv., Lief i. p. 47, pi. xx. fig. 3 (Ifigs. 1, 2, 4). 
Calamites Cistii, Renault, Cours. de botan. foss., vol. ii. p. 162, pi. xxiv. fig. 7, 1882. 

Remarks. — Not common, but extending throughout the whole of the Coal Measures 
Locality. — Streethead Pit, Galston. 
Horizon. — ? 

Calamocladus, Schimper. 
Calamocladus equisetiformis, Schloth., sp. 

Calamocladus equisetiformis, Schimper, Traite d. pale'ont. veget., vol. i. p. 324, pi. xxii. figs. 1, 2. 

Asterophyllites equisetiformis, Germar, Vers. v. Wettin u. Lobejun, p. 21, pi. viii. 

Asterophyllites equisetiformis, Zeiller, Flore foss. d. bassin houil. d. Valen., p. 368, pi. lviii. figs. 1-7. 

Asterophyllites equisetiformis, Zeiller, Veget. foss. d. terr. houil., p. 19, pi. clix. fig. 3. 

Asterophyllites equisetiformis, Geinitz, Vers. d. Steinkf. in Sachsen, p. 8, pi. xvii. fig. 1 (? figs. 2, 3). 

Asterophyllites equisetiformis, Goppert, Foss. Flora d. Perm. Form., p. 36, pi. i. fig. 5. 

Asterophyllites equisetiformis, Roehl, Foss. Flora d. Steink.-Form. Westph., p. 22, pi. iii. fig. 5. 

Asterophyllites equisetiformis, Weiss, Foss. Flora d. jiingst. Stic. u. Rothl., p. 126, pi. xii. fig. 2. 

Asterophyllites equisetiformis, Schenk in Richthofen's Cliina, vol. iv. p. 233, pi. xxxvii. fig. 3. 

Casuarinites equisetiformis, Schloth., Petrefactenk., p. 397. 

Anmdaria calamitoides, Schimper, Traite d. pale'ont. ve'get., vol. i. p. 349, pi. xxvi. fig. 1. 

Hippurites longifolia, L. and H., Fossil Flora, vol. iii. pis. cxc. cxci. 

Calamocladus binervis, Boulay, Terr, houil. du nord de la France et ses vegdt. foss., p. 22, pi. ii. fig. 1. 

Phytolithus (stellatus), Martin, Petrificata Derbiensia, pi. xx. figs. 4 and 6 {not fig. 5), 1809. 

Schlotheim, F